Acromegaly ,  age related macular degeneration ,  Alzheimer's disease ,  amyotrophic lateral sclerosis ,  autosomal dominant retinitis pigmentosa ,  beta thalassemia ,  cardiovascular disease , elevated level of  lipoprotein(a) , [ 33 ]   centronuclear myopathy ,  coagulopathies ,  cystic fibrosis ,  Duchenne muscular dystrophy ,  diabetes ,  epidermolysis bullosa dystrophica ,  familial chylomicronemia syndrome ,  frontotemporal dementia ,  Fuchs' dystrophy ,  hepatitis B ,  hereditary angioedema ,  hypertension ,  IgA nephropathy ,  Leber's hereditary optic neuropathy ,  multiple system atrophy ,  non-alcoholic fatty liver disease ,  Parkinson's disease ,  prostate cancer ,  Stargardt disease ,  STAT3-expressing   cancers ,  Usher syndrome .


Several ASOs are currently being investigated in disease models for  Alexander disease , [ 34 ]   ATXN2 (gene)  and  FUS (gene)   amyotrophic lateral sclerosis ,  Angelman syndrome , [ 35 ]   Lafora disease ,  lymphoma ,  multiple myeloma ,  myotonic dystrophy ,  Parkinson's disease , [ 36 ]   Pelizaeus–Merzbacher disease , [ 37 ] [ 38 ]  and  prion disease , [ 39 ]   Rett syndrome , [ 40 ]   spinocerebellar Ataxia Type 3 .


Assisted reproductive technology  ( ART ) includes medical procedures used primarily to address  infertility . This subject involves procedures such as  in vitro fertilization  (IVF),  intracytoplasmic sperm injection  (ICSI), and  cryopreservation  of gametes and embryos, and the use of  fertility medication . When used to address infertility, ART may also be referred to as  fertility treatment.  ART mainly belongs to the field of  reproductive endocrinology and infertility . Some forms of ART may be used with regard to fertile couples for genetic purpose (see  preimplantation genetic diagnosis ). ART may also be used in  surrogacy  arrangements, although not all surrogacy arrangements involve ART.
The existence of sterility will not always require ART to be the first option to consider, as there are occasions when its cause is a mild disorder that can be solved with more conventional treatments or with behaviors based on promoting health and reproductive habits.


With ART, the process of  sexual intercourse  is bypassed and fertilization of the  oocytes  occurs in the laboratory environment (i.e.,  in vitro fertilization ). [ citation needed ]


In the US, the  Centers for Disease Control and Prevention  (CDC) defines ART to include "all fertility treatments in which both eggs and sperm are handled. In general, ART procedures involve surgically removing eggs from a woman's ovaries, combining them with sperm in the laboratory, and returning them to the woman's body or donating them to another woman." According to CDC, "they do not include treatments in which only sperm are handled (i.e., intrauterine—or artificial—insemination) or procedures in which a woman takes medicine only to stimulate egg production without the intention of having eggs retrieved." [ 1 ]


In Europe, ART also excludes artificial insemination and includes only procedures where oocytes are handled. [ 2 ] [ 3 ]


The  World Health Organization  (WHO), also defines ART this way. [ 4 ]


Ovulation induction  is usually used in the sense of stimulation of the development of  ovarian follicles [ 5 ] [ 6 ] [ 7 ]  by  fertility medication  to reverse  anovulation  or  oligoovulation . These medications are given by injection for 8 to 14 days. A health care provider closely monitors the development of the eggs using transvaginal ultrasound and blood tests to assess follicle growth and estrogen production by the ovaries. When follicles have reached an adequate size and the eggs are mature enough, an injection of the hormone hCG initiates the ovulation process. Egg retrieval should occur 36 hours before ovulation.


In vitro fertilization  is the technique of letting  fertilization  of the male and female  gametes  (sperm and egg) occur outside the female body.


Techniques usually used in in vitro fertilization include:


Less commonly used techniques in in vitro fertilization are:


A  pre-implantation genetic diagnosis  procedure may be conducted on  embryos  prior to  implantation  (as a form of  embryo profiling ), and sometimes even of  oocytes  prior to  fertilization . PGD is considered in a similar fashion to  prenatal diagnosis . PGD is an adjunct to ART procedures, and requires in vitro fertilization to obtain  oocytes  or  embryos  for evaluation. Embryos are generally obtained through blastomere or blastocyst biopsy. The latter technique has proved to be less deleterious for the embryo, therefore it is advisable to perform the biopsy around day 5 or 6 of development. [ 9 ]   Sex selection  is the attempt to control the sex of offspring to achieve a desired sex in case of X chromosome linked diseases. It can be accomplished in several ways, both pre- and post-implantation of an embryo, as well as at birth. Pre-implantation techniques include PGD, but also  sperm sorting . [ citation needed ]


Other assisted reproduction techniques include:


The majority of IVF-conceived infants do not have  birth defects . [ 13 ]
However, some studies have suggested that assisted reproductive technology is associated with an increased risk of birth defects. [ 14 ] [ 15 ]
Artificial reproductive technology is becoming more available. Early studies suggest that there could be an increased risk for medical complications with both the mother and baby. Some of these include low birth weight, placental insufficiency, chromosomal disorders, preterm deliveries, gestational diabetes, and  pre-eclampsia  (Aiken and Brockelsby). [ 16 ]


In the largest U.S. study, which used data from a statewide registry of birth defects, [ 17 ]
6.2% of IVF-conceived children had major defects, as compared with 4.4% of naturally conceived children matched for  maternal age  and other factors ( odds ratio , 1.3; 95%  confidence interval , 1.00 to 1.67). [ 13 ]  ART carries with it a risk for  heterotopic pregnancy  (simultaneous intrauterine and extrauterine pregnancy). [ 18 ]
The main risks are:


Sperm donation  is an exception, with a birth defect rate of almost a fifth compared to the general population. It may be explained by that sperm banks accept only people with high sperm count.


Germ cells  of the mouse normally have a frequency of spontaneous point  mutations  that is 5 to 10-fold lower than that in  somatic cells  from the same individual. [ 22 ]   This low frequency in the  germline  leads to  embryos  that have a low frequency of point mutations in the next generation.  No significant differences were observed in the frequency or spectrum of mutations between naturally conceived fetuses and assisted-conception fetuses. [ 22 ]   This suggests that with respect to the maintenance of genetic integrity assisted conception is safe. [ 22 ]


Current data indicate little or no increased risk for  postpartum depression  among women who use ART. [ 23 ]


Study results indicate that ART can affect both women and men's sexual health negatively. [ 24 ]


Usage of assisted reproductive technology including  ovarian stimulation  and  in vitro fertilization  have been associated with an increased overall risk of  childhood cancer  in the offspring, which may be caused by the same original disease or condition that caused the infertility or subfertility in the mother or father. [ 25 ]


That said, In a landmark paper by Jacques Balayla et al. it was determined that infants born after ART have similar neurodevelopment than infants born after natural conception. [ 26 ]


ART may also pose risks to the mother. A large US database study compared pregnancy outcomes among 106,000 assisted conception pregnancies with 34 million natural conception pregnancies. It found that assisted conception pregnancies were associated with an increased risk of  cardiovascular diseases , including  acute kidney injury  and  arrhythmia . Assisted conception pregnancies were also associated with a higher risk of  caesarean delivery  and  premature birth . [ 27 ] [ 28 ]


In theory, ART can solve almost all reproductive problems, except for severe pathology or the absence of a uterus (or womb), using specific gamete or embryo donation techniques. However, this does not mean that all women can be treated with assisted reproductive techniques, or that all women who are treated will achieve pregnancy.


As a result of the 1992 Fertility Clinic Success Rate and Certification Act, the CDC is required to publish the annual ART success rates at U.S. fertility clinics. [ 29 ]  Assisted reproductive technology procedures performed in the U.S. has over than doubled over the last 10 years, with 140,000 procedures in 2006, [ 30 ]  resulting in 55,000 births. [ 30 ]


In  Australia , 3.1% of births in the late 2000's are a result of ART. [ 31 ]


The most common reasons for discontinuation of fertility treatment have been estimated to be: postponement of treatment (39%), physical and psychological burden (19%), psychological burden (14%), physical burden (6.32%), relational and personal problems (17%), personal reasons (9%), relational problems (9%), treatment rejection (13%) and organizational (12%) and clinic (8%) problems. [ 32 ]


Many Americans do not have  insurance  coverage for fertility investigations and treatments. Many states are starting to mandate coverage, and the rate of use is 278% higher in states with complete coverage. [ 33 ]


There are some health insurance companies that cover diagnosis of infertility, but frequently once diagnosed will not cover any treatment costs. [ citation needed ]


Approximate treatment/diagnosis costs in the United States, with inflation, as of 2023 (US$):


Another way to look at costs is to determine the expected cost of establishing a pregnancy. Thus, if a clomiphene treatment has a chance to establish a pregnancy in 8% of cycles and costs $780, the expected cost is $9,400 to establish a pregnancy, compared to an IVF cycle (cycle fecundity 40%) with a corresponding expected cost of $46,800 ($18,700 × 40%). [ citation needed ]


For the community as a whole, the cost of IVF on average pays back by 700% by tax from future employment by the conceived human being. [ 34 ]


In  Europe , 157,500 children were born using assisted reproductive technology in 2015, according to the  European Society of Human Reproduction and Embryology  (ESHRE). [ 35 ]  But there are major differences in legislation across the Old Continent.
A  European directive  fixes standards concerning the use of human tissue and cells, [ 37 ]  but all ethical and legal questions on ART remain the prerogative of  EU member states .


Across Europe, the legal criteria per availability vary somewhat. [ 39 ]  In 11 countries all women may benefit; in 8 others only heterosexual couples are concerned; in 7 only single women; and in 2 ( Austria  and  Germany ) only lesbian couples.
 Spain  was the first European country to open ART to all women, in 1977, the year the first sperm bank was opened there. In  France , the right to ART is accorded to all women since 2019. In the last 15 years, legislation has evolved quickly. For example,  Portugal  made ART available in 2006 with conditions very similar to those in France, before amending the law in 2016 to allow lesbian couples and single women to benefit.  Italy  clarified its uncertain legal situation in 2004 by adopting Europe's strictest laws: ART is only available to heterosexual couples, married or otherwise, and sperm donation is prohibited.


Today, 21 countries provide partial public funding for ART treatment. The seven others, which do not, are  Ireland ,  Cyprus ,  Estonia ,  Latvia ,  Luxembourg ,  Malta , and  Romania .
Such subsidies are subject to conditions, however. In  Belgium , a fixed payment of €1,073 is made for each full cycle of the IVF process. The woman must be aged under 43 and may not carry out more than six cycles of ART. There is also a limit on the number of transferable embryos, which varies according to age and the number of cycles completed.
In France, ART is subsidized in full by national health insurance for women up to age 43, with limits of 4 attempts at IVF and 6 at artificial insemination.
 Germany  tightened its conditions for public funding in 2004, which caused a sharp drop in the number of ART cycles carried out, from more than 102,000 in 2003 to fewer than 57,000 the following year. Since then the figure has remained stable.


17 countries limit access to ART according to the age of the woman. 10 countries have established an upper age limit, varying from 40 ( Finland ,  Netherlands ) to 50 (including Spain,  Greece  and Estonia).
Since 1994, France is one of a number of countries (including Germany, Spain, and the UK) which use the somewhat vague notion of "natural age of procreation". In 2017, the steering council of France's Agency of Biomedicine established an age limit of 43 for women using ART.
10 countries have no age limit for ART. These include Austria,  Hungary , Italy and  Poland .


Most European countries allow donations of gametes by third parties. But the situations vary depending on whether sperm or eggs are concerned. Sperm donations are authorized in 20 EU member states; in 11 of them anonymity is allowed. Egg donations are possible in 17 states, including 8 under anonymous conditions.
On 12 April, the  Council of Europe  adopted a recommendation which encourages an end to anonymity. [ 40 ]  In the UK, anonymous sperm donations ended in 2005 and children have access to the identity of the donor when they reach adulthood.
In France, the principle of anonymous donations of sperm or embryos is maintained in the law of bioethics of 2011, but a new bill under discussion may change the situation. [ 41 ]


In the United Kingdom, all patients have the right to preliminary testing, provided free of charge by the  National Health Service  (NHS). However, treatment is not widely available on the NHS and there can be long waiting lists. Many patients therefore pay for immediate treatment within the NHS or seek help from private clinics.


In 2013, the  National Institute for Health and Care Excellence  (NICE) published new guidelines about who should have access to IVF treatment on the NHS in England and Wales. [ 42 ]


The guidelines say women aged between 40 and 42 should be offered one cycle of IVF on the NHS if they have never had IVF treatment before, have no evidence of low ovarian reserve (this is when eggs in the ovary are low in number, or low in quality), and have been informed of the additional implications of IVF and pregnancy at this age. However, if tests show IVF is the only treatment likely to help them get pregnant, women should be referred for IVF straight away.


This policy is often modified by local  Clinical Commissioning Groups , in a fairly blatant breach of the  NHS Constitution for England  which provides that patients have the right to drugs and treatments that have been recommended by NICE for use in the NHS. For example, the Cheshire, Merseyside and West Lancashire Clinical Commissioning Group insists on additional conditions: [ 43 ]


Some treatments are covered by  OHIP  (public health insurance) in Ontario and others are not. Women with bilaterally blocked fallopian tubes and are under the age of 40 have treatment covered but are still required to pay test fees (around CA$3,000–4,000). Coverage varies in other provinces. Most other patients are required to pay for treatments themselves. [ 44 ]


Israel's national health insurance, which is mandatory for all Israeli citizens, covers nearly all fertility treatments. IVF costs are fully subsidized up to the birth of two children for all Israeli women, including single women and lesbian couples. Embryo transfers for purposes of gestational surrogacy are also covered. [ 45 ]


On 27 January 2009, the  Federal Constitutional Court  ruled that it is unconstitutional, that the health insurance companies have to bear only 50% of the cost for IVF. [ 46 ]  On 2 March 2012, the  Federal Council  has approved a draft law of some federal states, which provides that the federal government provides a subsidy of 25% to the cost. Thus, the share of costs borne for the pair would drop to just 25%. [ 47 ]  Since July 2017, assisted reproductive technology is also allowed for married lesbian couples, as German parliament allowed  same-sex marriages in Germany .


In July 2020, the  French Parliament  allowed assisted reproductive technology also for lesbian couples and single women. [ 48 ] [ 49 ]


Cuban sources mention that assisted reproduction is completely legal and free in the country. [ 50 ] [ 51 ]


The Government of India has notified the Surrogacy (Regulation) Act 2021 and the Assisted Reproductive Technology (Regulation) Act 2021 [ 52 ]  to regulate the practice of ART. Prior to that, the National Guidelines for Accreditation, Supervision and Regulation of ART Clinics in India published by the Ministry for Health and Family Welfare, Government of India in the year 2005 was governing the field. [ 53 ]  Indian law recognises the right of a single woman, who is a major, to have children through ART. [ 54 ]


Some couples may find it difficult to stop treatment despite very bad prognoses, resulting in futile therapies. This has the potential to give ART providers a difficult decision of whether to continue or refuse treatment. [ 55 ]


Some assisted reproductive technologies have the potential to be harmful to both the mother and the child, posing a psychological or physical health risk, which may affect the ongoing use of these treatments.


In Israel, there is research supporting using ART, including recycled lab materials from the IVF process, to help women work through some of these mixed emotions. [ 56 ] [ 57 ] [ 58 ] [ 59 ]


Films and other fiction depicting emotional struggles of assisted reproductive technology have had an upswing in the latter part of the 2000s decade, although the techniques have been available for decades. [ 60 ]  As ART becomes more utilized, the number of people that can relate to it by personal experience in one way or another is growing. [ 60 ]


For specific examples, refer to the fiction sections in individual subarticles, e.g.  surrogacy ,  sperm donation  and  fertility clinic .


In addition,  reproduction and pregnancy in speculative fiction  has been present for many decades.


25 July 1978,  Louise Brown  was born; this was the first successful birth of a child after  IVF  treatment. The procedure took place at Dr Kershaw's Cottage Hospital (now Dr Kershaw's Hospice) in Royton, Oldham, England.  Patrick Steptoe  (gynaecologist) and  Robert Edwards (physiologist)  worked together to develop the IVF technique. [ 61 ]  Steptoe described a new method of egg extraction and Edwards were carrying out a way to fertilise eggs in the lab. Robert G. Edwards was awarded the  Nobel Prize in Physiology or Medicine  in 2010, but not Steptoe because the Nobel Prize is not awarded posthumously. [ 62 ]


The first successful birth by ICSI ( intracytoplasmic sperm injection ) took place on 14 January 1992. The technique was developed by  Gianpiero D. Palermo  at the  Vrije Universiteit Brussel , in the Center for Reproductive Medicine in Brussels. Actually, the discovery was made by a mistake when a spermatozoid was put into the cytoplasm. [ 63 ]


This article incorporates text from a  free content  work. Licensed under CC BY 4.0. Text taken from  How does assisted reproductive technology work in Europe? , Orlane Jézéquélou/Alternatives Economiques, EDJNet.


Bac ulovirus  gene transfer  into  Mam malian cells (BacMam) is the use of a  baculovirus  to deliver  genes  to  mammalian  cells. [ 1 ] [ 2 ]  Baculoviruses are insect viruses that are typically not capable of infecting mammalian cells; however, they can be modified to express  proteins  in  mammalian  cells. Unmodified baculoviruses are able to enter mammalian cells; however, their genes are not expressed unless a recognizable mammalian  promoter  is incorporated upstream of a gene of interest. Both the unmodified baculovirus and its modified counterpart are unable to replicate in  humans , making them non-infectious.


Baculovirus-mediated gene transfer was developed by Dr. Frederick M. Boyce. [ 3 ]  It has gained widespread use because of certain advantages compared to other  transfection  methods. [ 4 ] [ 5 ] [ 6 ]  BacMam has been found to have some stability and flexibility over other  cell line  methods, [ 7 ]  which has contributed to its adoption as a standard gene transfer technique.


The BacMam gene delivery technology is a transient expression system, which facilitates the expression of gene products. It has a broad range of transduction, including many primary cell types and  stem cells . [ 8 ]  The baculoviral genome has a large capacity for the insertion of foreign genes, with insertions of up to 38 kb having been successfully tested. [ 9 ]  Simultaneous delivery of multiple genes to the same cell is feasible. [ 10 ]  There are little to no microscopically observable cytopathic effects of BacMam particles on mammalian cells. [ 11 ]  The level of gene expression can be adjusted by viral dose or chemical additions using histone deacetylase inhibitors. [ 12 ]  Transduction of cells is performed by liquid-only addition, making BacMam amenable to automated methods. Viruses are stable when stored at 4 °C in the dark for long periods of time. [ 13 ]


Baculoviruses are  Risk Group 1  agents that have been widely used for over 25 years for insect cell  protein production  applications. [ 14 ]  Baculoviruses are produced in insect cells and incapable of replicating in mammalian cells and are not known to cause disease in healthy human adults. Furthermore, BacMam viruses are inactivated by human complement, which reduces risk to researchers. Viruses used in the laboratory are unable to replicate in insects, so there is no environmental threat if these particles were to be released into the environment. [ 15 ] [ 16 ]


Studies on baculovirus entry into human  hepatocellular carcinoma  cells suggest that BacMam enters mammalian cells via clathrin-mediated  endocytosis  and possibly via  micropinocytosis . [ 17 ]  Further studies have suggested that  caveolae  are involved in baculovirus entry in mammalian cells. [ 18 ]


To be effective, a gene delivery technology must not interfere with normal cellular function.  Cytotoxicity  assays and transcriptome analyses on a human  HEK cell  line (HEK293) have revealed that baculovirus transduction is not cytotoxic and does not induce differential transcriptional responses. [ 19 ]  Similarly, infected  Schwann cells  retain their characteristic morphological and molecular  phenotype  and are capable of differentiating in vitro and expressing the P0  myelination  marker. Using  complementary DNA  (cDNA) microarray technology to examine  in vitro  and  in vivo  global cellular gene expression profiles in the rat brain, cultured human  astrocytes , and human neuronal cells after viral transduction, host antiviral responses were observed. [ 20 ]  The related genes were mainly those associated with innate immunity, including several of the genes involved in  Toll-like receptor  signaling pathway and  cytokine -cytokine receptor interaction.


BacMam has been used to produce proteins in large quantities using HEK293 cells in a  hollow fiber bioreactor  system. [ 21 ]


Pharmacology of G protein-coupled receptor can be studied using BacMam technology in  drug discovery  applications. [ 22 ]


Organelle labeling reagents are commercially available BacMam particles for labeling organelles and other subcellular structures [ 23 ]  Single mitochondrion labeling with a mitochondrial targeted green fluorescent protein. [ 24 ]


Characterization of serotonin receptor activation via a BacMam delivered GFP fusion to a kinase substrate has been performed. [ 25 ]


The BacMam system can  be used to produce soluble and membrane-situated glycoproteins for structural studies. [ 26 ]


A  biobank  is a type of  biorepository  that stores biological samples (usually human) for use in research. Biobanks have become an important resource in medical research, supporting many types of contemporary research like  genomics  and  personalized medicine .


Biobanks can give researchers access to data representing a large number of people. Samples in biobanks and the data derived from those samples can often be used by multiple researchers for cross purpose research studies. For example, many diseases are associated with  single-nucleotide polymorphisms .  Genome-wide association studies  using data from tens or hundreds of thousands of individuals can identify these genetic associations as potential disease  biomarkers . Many researchers struggled to acquire sufficient samples prior to the advent of biobanks.


Biobanks have provoked questions on privacy,  research ethics , and  medical ethics . Viewpoints on what constitutes appropriate  biobank ethics  diverge. However, a consensus has been reached that operating biobanks without establishing carefully considered governing principles and policies could be detrimental to communities that participate in biobank programs.


The term "biobank" first appeared in the late 1990s and is a broad term that has evolved in recent years. [ 1 ] [ 2 ]  One definition is "an organized collection of human biological material and associated information stored for one or more research purposes." [ 3 ] [ 4 ]   Collections of plant, animal, microbe, and other nonhuman materials may also be described as biobanks but in some discussions the term is reserved for human specimens. [ 3 ]


Biobanks usually incorporate  cryogenic  storage facilities for the samples. [ 5 ]   They may range in size from individual refrigerators to warehouses, and are maintained by institutions such as hospitals, universities, nonprofit organizations, and pharmaceutical companies. [ 5 ]


Biobanks may be classified by purpose or design. Disease-oriented biobanks usually have a hospital affiliation through which they collect samples representing a variety of diseases, perhaps to look for biomarkers affiliated with disease. [ 6 ] [ 7 ]  Population-based biobanks need no particular hospital affiliation because they take samples from large numbers of all kinds of people, perhaps to look for biomarkers for disease susceptibility in a general population. [ 8 ]


In 2008, United States researchers stored 270 million specimens in biobanks, and the rate of new sample collection was 20 million per year. [ 11 ]  These numbers represent a fundamental worldwide change in the nature of research between the time when such numbers of samples could not be used and the time when researchers began demanding them. [ 11 ]  Collectively, researchers began to progress beyond single-center research centers to a next-generation qualitatively different research infrastructure. [ 12 ]  Some of the challenges raised by the advent of biobanks are ethical, legal, and social issues pertaining to their existence, including the fairness of collecting donations from vulnerable populations, providing  informed consent  to donors, the logistics of data disclosure to participants, the right to ownership of intellectual property, and the privacy and security of donors who participate. [ 11 ]  Because of these new problems, researchers and policymakers began to require new systems of research governance. [ 12 ]


Many researchers have identified biobanking as a key area for infrastructure development in order to promote  drug discovery  and  drug development . [ 3 ]


By the late 1990s, scientists realized that although many diseases are caused at least in part by a genetic component, few diseases originate from a single defective  gene ; most genetic diseases are caused by multiple genetic factors on multiple genes. [ 13 ]  Because the strategy of looking only at single genes was ineffective for finding the genetic components of many diseases, and because new technology made the cost of examining a single gene versus doing a genome-wide scan about the same, scientists began collecting much larger amounts of genetic information when any was to be collected at all. [ 13 ]  At the same time technological advances also made it possible for wide sharing of information, so when data was collected, many scientists doing genetics work found that access to data from genome-wide scans collected for any one reason would actually be useful in many other types of genetic research. [ 13 ]  Whereas before data usually stayed in one laboratory, now scientists began to store large amounts of genetic data in single places for community use and sharing. [ 13 ]


An immediate result of doing genome-wide scans and sharing data was the discovery of many  single-nucleotide polymorphisms , with an early success being an improvement from the identification of about 10,000 of these with single-gene scanning and before biobanks versus 500,000 by 2007 after the genome-wide scanning practice had been in place for some years. [ 13 ]  A problem remained; this changing practice allowed the collection of  genotype  data, but it did not simultaneously come with a system to gather the related  phenotype  data. [ 13 ]  Whereas genotype data comes from a biological specimen like a blood sample, phenotype data has to come from examining a specimen donor with an interview, physical assessment, review of medical history, or some other process which could be difficult to arrange. [ 13 ]  Even when this data was available, there were ethical uncertainties about the extent to which and the ways in which patient rights could be preserved by connecting it to genotypic data. [ 13 ]  The institution of the biobank began to be developed to store genotypic data, associate it with phenotypic data, and make it more widely available to researchers who needed it. [ 13 ]


Biobanks including  genetic testing  samples have historically been composed of a majority of samples from individuals from European ancestry. [ 14 ]  Diversification of biobank samples is needed and researchers should consider the factors effecting the underrepresented populations. [ 15 ] [ 16 ]


In November 2020 scientists began collecting living fragments, tissue and DNA samples of the endangered corals from the  Great Barrier Reef  for a precautionary biobank for potential future  restoration  and rehabilitation activities. [ 17 ]  A few months earlier another Australian team of researchers reported that they evolved such corals to be more heat-resistant. [ 18 ]


The  specimens  stored by a biobank and made available to researchers are taken by  sampling . Specimen types include  blood ,  urine , skin cells, organ tissue, and other materials. Increasingly, methods for sampling tissue specimens are becoming more targeted, sometimes involving the use of  MRI  to determine which specific areas of tissue should be sampled. [ 19 ] [ 20 ]  The biobank keeps these specimens in good condition until a researcher needs them to conduct a test, do an experiment, or perform an analysis. [ citation needed ]


Biobanks, like other DNA databases, must carefully store and document access to samples and donor information. [ 21 ]  The samples must be maintained reliably with minimal deterioration over time, and they must be protected from physical damage, both accidental and intentional. The registration of each sample entering and exiting the system is centrally stored, usually on a computer-based system that can be backed up frequently. [ 21 ]  The physical location of each sample is noted to allow the rapid location of specimens. Archival systems de-identify samples to respect the privacy of donors and allow blinding of researchers to analysis. [ 21 ]  The database, including clinical data, is kept separately with a secure method to link clinical information to tissue samples. [ 21 ]  Room temperature storage of samples is sometimes used, and was developed in response to perceived disadvantages of low-temperature storage, such as costs and potential for freezer failure. [ 21 ]   Current systems are small and are capable of storing nearly 40,000 samples in about one tenth of the space required by a −80 °C (−112 °F) freezer. Replicates or split samples are often stored in separate locations for security. [ 21 ]


One controversy of large databases of genetic material is the question of ownership of samples. As of 2007,  Iceland  had three different laws on ownership of the physical samples and the information they contain. [ 22 ]  Icelandic law holds that the Icelandic government has custodial rights of the physical samples themselves while the donors retain ownership rights. [ 22 ]  In contrast,  Tonga  and  Estonia  give ownership of biobank samples to the government, but their laws include strong protections of donor rights. [ 22 ]


The key event which arises in biobanking is when a researcher wants to collect a human specimen for research. When this happens, some issues which arise include the following: right to  privacy for research participants , ownership of the specimen and its derived data, the extent to which the donor can share in the  return of the research results , and the extent to which a donor is able to consent to be in a research study. [ 23 ]


With respect to consent, the main issue is that biobanks usually collect samples and data for multiple future research purposes and it is not feasible to obtain specific consent for all possible future research. It has been discussed that one-off consent or a broad consent for various research purposes may not suffice ethical and legal requirements. [ 24 ] [ 25 ]   Dynamic consent  is an approach to consent that may be better suited to biobanking, because it enables ongoing engagement and communication between the researchers and sample/data donors over time.


There is no internationally accepted set of governance guidelines that are designed to work with biobanks. Biobanks typically try to adapt to the broader recommendations that are internationally accepted for human subject research and change guidelines as they become updated. For many types of research and particularly medical research, oversight comes at the local level from an  institutional review board . Institutional review boards typically enforce standards set by their country's government. To different extents, the law used by different countries is often modeled on biobank governance recommendations that have been internationally proposed.


Some examples of organizations that participated in creating written biobanking guidelines are the following: [ 2 ]   World Medical Association ,  Council for International Organizations of Medical Sciences ,  Council of Europe ,  Human Genome Organisation ,  World Health Organization , and  UNESCO .
The International Society for Biological and Environmental Repositories (ISBER) is a global biobanking organization which creates opportunities for networking, education, and innovations and harmonizes approaches to evolving challenges in biological and environmental repositories. ISBER connects repositories globally through best practices. The ISBER Best Practices, Fourth Edition was launched on January 31, 2018 with a LN2 addendum that was launched early May 2019. [ 26 ]


In 1998, the  Icelandic Parliament  passed the  Act on Health Sector Database . This act allowed for the creation of a national biobank in that country. In 1999, the United States  National Bioethics Advisory Commission  issued a report containing policy recommendations about handling human biological specimens. [ 11 ]  In 2005, the United States  National Cancer Institute  founded the  Office of Biorepositories and Biospecimen Research  so that it could have a division to establish a common database and standard operating procedures for its partner organizations with biospecimen collections. [ 11 ]  In 2006, the  Council of the European Union  adopted a policy on human biological specimens, which was novel for discussing issues unique to biobanks. [ 11 ]


Researchers have called for a greater critical examination of the economic aspects of Biobanks, particularly those facilitated by the state. [ 27 ]  National biobanks are often funded by public/private partnerships, with finance provided by any combination of national research councils, medical charities, pharmaceutical company investment, and biotech venture capital. [ 28 ]  In this way, national biobanks enable an economic relationship mediated between states, national populations, and commercial entities. It has been illustrated that there is a strong commercial incentive underlying the systematic collection of tissue material. This can be seen particularly in the field of genomic research where population sized study lends itself more easily toward diagnostic technologies rather than basic etiological studies. [ 29 ]  Considering the potential for substantial profit, researchers Mitchell and  Waldby [ 27 ]  argue that because biobanks enroll large numbers of the national population as productive participants, who allow their bodies and prospective medical histories to create a resource with commercial potential, their contribution should be seen as a form of "clinical labor" and therefore participants should also benefit economically.


There have been cases when the ownership of stored human specimens have been disputed and taken to court.  Some cases include:


Biodistribution  is a method of tracking where compounds of interest travel in an experimental animal or human subject.  For example, in the development of new compounds for PET ( positron emission tomography ) scanning, a  radioactive isotope  is chemically joined with a  peptide  (subunit of a  protein ).  This particular class of isotopes emits  positrons  (which are  antimatter  particles, equal in mass to the electron, but with a positive charge).  When ejected from the nucleus, positrons encounter an electron, and undergo  annihilation  which produces two  gamma rays  travelling in opposite directions.  These gamma rays can be measured, and when compared to a standard, quantified.


A useful novel  radiolabelled  compound is one that is suitable either for  medical imaging  of certain body parts such as brain or tumors (injecting low doses of radioactivity) or for treating tumors (requiring injection of high doses of radioactivity). In both cases, the compound needs to accumulate in the target organ and any surplus compound present needs to clear the body rapidly. In medical diagnostic imaging, this then produces a clear diagnostic image (high image contrast), and in radiotherapy leads to an attack of the target (e.g. tumor) while minimizing side effects to non-target organs. Additional factors need to be evaluated in the development of a new diagnostic or therapeutic compound, including safety for humans. From an efficacy point of view, the biodistribution is an important aspect which can be measured by dissection or by imaging.


For example, a new radiolabelled compound is injected intravenously into a group of 16-20 rodents (typically mice or rats).  At intervals of 1, 2, 4, and 24 hours, smaller groups (4-5) of the animals are euthanized, then dissected.  The organs of interest (usually: blood, liver, spleen, kidney, muscle, fat, adrenals, pancreas, brain, bone, stomach, small intestine, and upper and lower large intestine, a tumor if present) are placed in pre-weighed containers and weighed, then placed into a device that measures radioactivity (e.g. gamma radiation). Normalizing the tissue radioactivity concentrations to the injected dose gives values in units of percent of the injected dose per gram of organ or biological tissue. The results give a dynamic view of how the compound moves through the animal and where it is retained.


Similar to the dissection procedure, animals are injected with a low dose of a radiolabelled compound. At the chosen time points after injection, PET or SPECT images are acquired, typically also a CT or MR image for anatomical reference. The radioactivity concentration is measured from the PET or SPECT images for the various organs of interest. This may include measuring the volume of these organs e.g. from the CT image (rather than weighing the organs as in the dissection procedure) or assessing the radioactivity concentration in a representative part of the organ. Normalizing the tissue radioactivity concentrations to the injected dose gives values in units of percent of the injected dose per milliliter of organ or biological tissue.


A benefit of imaging is that the animals can be anaesthetized for imaging for several or all the required time points, that is few animals are required for this procedure and all of them are kept alive. This is considered a non-invasive procedure. In addition, the procedure is in essence the same as for medical diagnostic imaging in the clinic with two main differences: (1) novel compounds under development may be injected into animals subject to scrutiny and approval of the detailed experimental plan while clinicians can only inject radiolabelled compounds that had been tested rigorously and approved for use in humans; (2) animals usually need to be anaesthetized for the duration of the scan (on the order of minutes) while humans are awake and simply need to stay still during the scan.


In  gene therapy , gene delivery vectors, such as viruses, can be imaged according either to their particle biodistribution or their  transduction  pattern. The former means labeling the viruses with a  contrast agent , being visible in some imaging modality, such as  MRI  or  SPECT / PET  and latter means visualising the  marker gene  of gene delivery vector to be visible by the means of immunohistochemical methods,  optical imaging  or even by  PCR . Non-invasive imaging has gained popularity as the imaging equipment has become available for research use from clinics.


For example,  avidin -displaying  baculoviruses  could be imaged in rat brain by coating them with biotinylated iron particles, rendering them visible in MR imaging. The biodistribution of the iron-virus particles was seen to concentrate on the  choroid plexus  cells of lateral ventricles. [ 1 ]


Cationic liposomes  are spherical structures that contain positively charged  lipids . Cationic  liposomes  can vary in size between 40 nm and 500 nm, and they can either have one  lipid bilayer  (monolamellar) or multiple lipid bilayers (multilamellar). [ 1 ]  The positive charge of the  phospholipids  allows cationic liposomes to form complexes with negatively charged nucleic acids ( DNA ,  mRNA , and  siRNA ) through  ionic  interactions. Upon interacting with nucleic acids, cationic liposomes form clusters of aggregated vesicles. [ 2 ]  These interactions allow cationic liposomes to condense and encapsulate various therapeutic and diagnostic agents in their aqueous compartment or in their lipid bilayer. [ 3 ] [ 4 ]  These cationic liposome-nucleic acid complexes are also referred to as  lipoplexes . Due to the overall positive charge of cationic liposomes, they interact with negatively charged  cell membranes  more readily than classic liposomes. [ 3 ]  This positive charge can also create some issues  in vivo , such as binding to plasma proteins in the bloodstream, which leads to opsonization. [ 5 ]  These issues can be reduced by optimizing the physical and chemical properties of cationic liposomes through their lipid composition. [ 5 ]  Cationic liposomes are increasingly being researched for use as  delivery vectors  in  gene therapy  due to their capability to efficiently transfect cells. [ 3 ] [ 4 ]  A common application for cationic liposomes is cancer drug delivery. [ 3 ]


In the 1960s,  Alec D. Bangham  discovered liposomes as concentric lipid bilayers surrounding an  aqueous  center, based on his research at the University of Cambridge Babraham Institute. [ 6 ] [ 7 ]  The first  formulations  were designed using all natural  lipids . [ 6 ]  In 1987, Philip Felgner published the first approach to using cationic lipids to  transfect  DNA into cells, [ 8 ]  based on his research into cationic lipids at  Syntex  from 1982 to 1988. [ 9 ]  Felgner introduced the first cationic lipid used for gene delivery,  N -[1-(2,3-dioleyloxy)propyl]- N , N , N -trimethylammonium chloride (DOTMA). [ 10 ]


The use of cationic lipids helps to enhance the overall stability and efficiency of liposomes. Although cationic lipids themselves are able to encapsulate nucleic acids into liposomes, the  transfection  efficiency is low due to a process known as  endosomal  escape. Lipids that are capable of destabilizing endosomal membranes and facilitating endosomal escape are known as fusogenic lipids. The addition of helper lipids to the cationic lipids demonstrates a much higher transfection efficiency. [ 3 ]


Cationic liposomes with a higher transfection efficiency are composed of a cationic phospholipid, and a few neutral helper lipids. A commonly used cationic phospholipid is DOTMA, and a commonly used fusogenic helper lipid is dioleoyl phosphatidylethanolamine (DOPE). A couple of commonly used neutral helper lipids are  cholesterol  and  polyethylene glycol (PEG) -lipid. [ 3 ]  These components are all biocompatible and biodegradable in the human body, making cationic liposomes a useful gene delivery vector. [ 6 ]


Because the phospholipids each have a  hydrophobic  tail and a  hydrophilic  head group, they are able to form a lipid bilayer with the hydrophilic heads facing outwards and the hydrophobic tails facing inwards. Adding DOPE in addition to DOTMA promotes the endosomal escape of nucleic acids into the cytosol when the cationic lipid is fused to an endosome membrane. [ 3 ]  The addition of  cholesterol  helps to stabilize the liposome and more efficiently encapsulate nucleic acids. Regulating the structure and flexibility of the lipid bilayer with cholesterol allows for a more dense assembly of phospholipids. [ 5 ]  The PEG-lipid binds to the outer surface of the liposome, acting as a protective layer and reducing the formation of a protein corona. [ 3 ]  The presence of PEG on the surface of the liposome drastically increases the blood circulation time of cationic liposomes. [ 5 ] [ 6 ]


Cationic liposomes are manufactured similarly to  liposomes . There are multiple processes that can be used to form cationic liposomes, such as  sonication ,  extrusion , and  vortexing . However, the shear forces associated with these methods are capable of damaging the nucleic acids prior to encapsulation.  Microfluidics  is a field that is currently being looked into for the purpose of forming cationic liposomes without the shear forces and damage associated with current methods. [ 11 ]


Cationic liposomes can deliver nucleic acids into the cell through an endocytotic pathway or through cell membrane fusion. [ 3 ] [ 12 ]  Fusogenic cationic liposomes almost exclusively deliver nucleic acids through cell membrane fusion. [ 3 ]  The fusion between positively charged cationic liposomes and negatively charged cell surfaces efficiently delivers the DNA directly across the  plasma membrane . This process bypasses the  endosomal - lysosomal  route, which leads to the degradation of  anionic  liposome formulations. [ 13 ]  Cationic liposomes in the lamellar phase deliver nucleic acids through  endocytosis , specifically clathrin-mediated endocytosis (CME), caveolae-mediated endocytosis (CavME), and macropinocytosis. [ 3 ]


After administration  in vivo , cationic liposomes are biodegradable due to the presence of endogenous enzymes that can digest the lipids. [ 14 ]


Paclitaxel  (PTX) is a chemotherapy medication used to treat many types of cancer, such as ovarian cancer, breast cancer, and pancreatic cancer. [ 7 ]  PTX works by inhibiting the growth of tumor endothelial cells, however it has in vivo delivery issues that are caused by its unfavorable pharmacokinetic and physical properties. Studies have shown that some patients who take PTX experience adverse reactions, such as nephrotoxicity and neurotoxicity. [ 7 ] [ 15 ]


SynCore Bio's EndoTAG-1 is a cationic liposome formulation with embedded PTX. The cationic lipid used in this formulation is dioleoyloxypropyltrimethylammonium (DOTAP). [ 16 ]  The PTX-embedded cationic liposome interacts with the negatively charged tumor endothelial cells required for tumor  angiogenesis , in order to reduce their tumor blood supply. [ 7 ] [ 16 ]  Through this mechanism, EndoTAG-1 is able to prevent angiogenesis in the tumor, which in turn inhibits tumor growth. [ 16 ]  EndoTAG-1 is currently under phase III clinical trial investigation, and is specifically targeting adenocarcinoma of the pancreas when used in combination with  gemcitabine . [ 17 ]


The positive charge of cationic lipids has been shown to have  cytotoxic  effects, as these lipids can activate several  pro-apoptotic  and  pro-inflammatory   cell signaling pathways . [ 10 ]  The cationic nature of these lipids is associated with the structure of the head group. [ 10 ]  In particular, it was found that the quaternary ammonium head groups of some cationic lipids (e.g., DOTMA) are more cytotoxic than the peptide head groups of other cationic lipids. [ 10 ]  This cytotoxic effect can be reduced by the addition of PEG on the surface of the cationic liposome. [ 3 ] [ 5 ] [ 6 ]


If delivered through  intravenous administration , cationic liposomes can result in opsonization, which is an immune response that occurs when  opsonins  tag foreign pathogens to be eliminated through phagocytosis. [ 3 ] [ 18 ]  Due to their positive charge, cationic liposomes bind to various  plasma  proteins, forming a protein corona on their surface and completely changing their biological identity. [ 3 ]  This new biological identity then causes opsonins to tag them as pathogens and encourages clearance through phagocytic clearance. [ 3 ]


Chimeraplasty  is a non-viral method of  gene therapy . [ 1 ]  Chimeraplasty changes  DNA  sequences using a synthetic strand of  RNA  and DNA. This strand of RNA and DNA is known as a chimeraplast. The chimeraplast enters a  cell  and attaches itself to the target  gene . The DNA of the chimeraplast and the cell complement each other except in the middle of the strand, where the chimeraplast's sequence is different from that of the cell. The DNA repair enzymes then replace the cell's DNA with that of the chimeraplast. This leaves the chimeraplast's new sequence in the cell's DNA and the replaced DNA sequence then decays.


This technique was first developed and named by Eric Kmiec at  Thomas Jefferson University . Since its discovery there has been debate over chimeraplasty's effectiveness. In the 6 September 1996 article of  Science , Kmiec claimed that chimeraplasty was 50% effective in human cells. This figure was later disputed by a number of universities; chimeraplasty is now considered from .4-2.4% effective at transforming fibroblasts, [ 1 ]  and 0.0002% effective in transforming yeast cells. [ 2 ]


Chromosome microdissection  is a technique that physically removes a large section of  DNA  from a complete  chromosome . The smallest portion of DNA that can be isolated using this method comprises 10 million  base pairs  - hundreds or thousands of individual  genes .


Scientists who study chromosomes are known as  cytogeneticists . They are able to identify each chromosome based on its unique pattern of dark and light bands. Certain abnormalities, however, cause chromosomes to have unusual banding patterns. For example, one chromosome may have a piece of another chromosome inserted within it, creating extra bands. Or, a portion of a chromosome may be repeated over and over again, resulting in an unusually wide, dark band (known as a  homogeneously staining region ). Some chromosomal aberrations have been linked to  cancer  and inherited genetic disorders, and the chromosomes of many tumor cells exhibit irregular bands. To understand more about what causes these conditions, scientists hope to determine which genes and DNA sequences are located near these unusual bands. Chromosome microdissection is a specialized way of isolating these regions by removing the DNA from the band and making that DNA available for further study.


To prepare cells for chromosome microdissection, a scientist first treats them with a chemical that forces them into  metaphase : a phase of the cell's life-cycle where the chromosomes are tightly coiled and highly visible. Next, the cells are dropped onto a  microscope slide  so that the nucleus, which holds all of the genetic material together, breaks apart and releases the chromosomes onto the slide. Then, under a microscope, the scientist locates the specific band of interest, and, using a very fine needle, tears that band away from the rest of the chromosome. The researcher next produces multiple copies of the isolated DNA using a procedure called  PCR  ( polymerase chain reaction ). The scientist uses these copies to study the DNA from the unusual region of the chromosome in question.


Conservation genetics  is an  interdisciplinary  subfield of  population genetics  that aims to understand the dynamics of  genes  in a population for the purpose of  natural resource management , conservation of  genetic diversity , and the prevention of species  extinction . Scientists involved in conservation genetics come from a variety of fields including  population genetics , research in  natural resource management ,  molecular ecology ,  molecular biology ,  evolutionary biology , and  systematics . The  genetic diversity  within species is one of the three fundamental components of  biodiversity  (along with  species diversity  and  ecosystem diversity ), [ 1 ]  so it is an important consideration in the wider field of  conservation biology .


Genetic diversity  is the total amount of genetic variability within a species. It can be measured in several ways, including: observed  heterozygosity , expected heterozygosity, the mean number of  alleles  per  locus , the percentage of loci that are  polymorphic , and estimated  effective population size . Genetic diversity on the population level is a crucial focus for conservation genetics as it influences both the health of individuals and the long-term survival of populations: decreased genetic diversity has been associated with reduced average  fitness  of individuals, such as high juvenile mortality, reduced immunity, [ 2 ]  diminished population growth, [ 3 ]   and ultimately, higher extinction risk. [ 4 ] [ 5 ]


Heterozygosity , a fundamental measurement of genetic diversity in  population genetics , plays an important role in determining the chance of a population surviving environmental change, novel pathogens not previously encountered, as well as the average fitness within a population over successive generations. Heterozygosity is also deeply connected, in population genetics theory, to  population size  (which itself clearly has a fundamental importance to conservation). All things being equal, small populations will be less heterozygous   – across their whole genomes   – than comparable, but larger, populations. This lower heterozygosity (i.e. low genetic diversity) renders small populations more susceptible to the challenges mentioned above. [ 6 ]


In a small population, over successive generations and without  gene flow , the probability of mating with close relatives becomes very high, leading to  inbreeding depression   – a reduction in average fitness of individuals within a population. The reduced fitness of the offspring of closely related individuals is fundamentally tied to the concept of heterozygosity, as the offspring of these kinds of pairings are, by necessity, less heterozygous (more homozygous) across their whole genomes than outbred individuals. A diploid individual with the same maternal and paternal grandfather, for example, will have a much higher chance of being homozygous at any loci inherited from the paternal copies of each of their parents' genomes than would an individual with unrelated maternal and paternal grandfathers (each diploid individual inherits one copy of their genome from their mother and one from their father).


High homozygosity (low heterozygosity) reduces fitness because it exposes the phenotypic effects of recessive alleles at homozygous sites. Selection can favour the maintenance of alleles which reduce the fitness of homozygotes, the textbook example being the sickle-cell beta-globin allele, which is maintained at high frequencies in populations where malaria is endemic due to the highly adaptive heterozygous phenotype (resistance to the malarial parasite  Plasmodium falciparum ).


Low genetic diversity also reduces the opportunities for  chromosomal crossover  during  meiosis  to create new combinations of alleles on chromosomes, effectively increasing the average length of unrecombined tracts of chromosomes inherited from parents. This in turn reduces the efficacy of selection, across successive generations, to remove fitness-reducing alleles and promote fitness-enhancing alleles from a population. A simple hypothetical example would be two adjacent genes   – A and B   – on the same chromosome in an individual. If the allele at A promotes fitness "one point", while the allele at B reduces fitness "one point", but the two genes are inherited together, then selection cannot favour the allele at A while penalising the allele at B   – the fitness balance is "zero points". Recombination can swap out alternative alleles at A and B, allowing selection to promote the optimal alleles to the optimal frequencies in the population   – but only if there are alternative alleles to choose between.


The fundamental connection between genetic diversity and population size in population genetics theory can be clearly seen in the classic population genetics measure of genetic diversity, the  Watterson estimator , in which genetic diversity is measured as a function of  effective population size  and  mutation rate . Given the relationship between population size, mutation rate, and genetic diversity, it is clearly important to recognise populations at risk of losing genetic diversity before problems arise as a result of the loss of that genetic diversity. Once lost, genetic diversity can only be restored by  mutation  and gene flow. If a species is already on the brink of extinction there will likely be no populations to use to restore diversity by gene flow, and any given population will be small and therefore diversity will accumulate in that population by mutation much more slowly than it would in a comparable, but bigger, population (since there are fewer individuals whose genomes are mutating in a smaller population than a bigger population).


Specific genetic techniques are used to assess the genomes of a species regarding specific conservation issues as well as general population structure. [ 14 ]  This analysis can be done in two ways, with current DNA of individuals or historic DNA. [ 15 ]


Techniques for analysing the differences between individuals and populations include


These different techniques focus on different variable areas of the genomes within animals and plants. The specific information that is required determines which techniques are used and which parts of the genome are analysed. For example,  mitochondrial DNA  in animals has a high substitution rate, which makes it useful for identifying differences between individuals. However, it is only inherited in the female line, and the mitochondrial genome is relatively small. In plants, the mitochondrial DNA has very high rates of structural mutations, so is rarely used for genetic markers, as the  chloroplast genome  can be used instead. Other sites in the genome that are subject to high mutation rates such as the  major histocompatibility complex , and the  microsatellites  and  minisatellites  are also frequently used.


These techniques can provide information on long-term conservation of genetic diversity and expound demographic and ecological matters such as taxonomy. [ 14 ]


Another technique is using historic DNA for genetic analysis. Historic DNA is important because it allows geneticists to understand how species reacted to changes to conditions in the past. This is a key to understanding the reactions of similar species in the future. [ 15 ]


Techniques using historic DNA include looking at preserved remains found in museums and caves. [ 16 ]  Museums are used because there is a wide range of species that are available to scientists all over the world. The problem with museums is that, historical perspectives are important because understanding how species reacted to changes in conditions in the past is a key to understanding reactions of similar species in the future. [ 16 ]  Evidence found in caves provides a longer perspective and does not disturb the animals. [ 16 ]


Another technique that relies on specific genetics of an individual is noninvasive monitoring, which uses extracted DNA from organic material that an individual leaves behind, such as a feather. [ 16 ]  Environmental DNA (eDNA) can be extracted from soil, water, and air. Organisms deposit tissue cells into the environment and the degradation of these cells results in DNA being released into the environment. [ 17 ] This too avoids disrupting the animals and can provide information about the sex, movement, kinship and diet of an individual. [ 16 ]


Other more general techniques can be used to correct genetic factors that lead to extinction and risk of extinction. For example, when minimizing inbreeding and increasing genetic variation multiple steps can be taken. Increasing  heterozygosity  through immigration, increasing the generational interval through  cryopreservation  or breeding from older animals, and increasing the  effective population size  through equalization of family size all helps minimize inbreeding and its effects. [ 18 ]  Deleterious alleles arise through mutation, however certain recessive ones can become more prevalent due to inbreeding. [ 18 ]  Deleterious mutations that arise from inbreeding can be removed by  purging , or natural selection. [ 18 ]  Populations raised in captivity with the intent of being reintroduced in the wild suffer from adaptations to captivity. [ 19 ]


Inbreeding depression, loss of genetic diversity, and genetic adaptation to captivity are disadvantageous in the wild, and many of these issues can be dealt with through the aforementioned techniques aimed at increasing heterozygosity. In addition creating a captive environment that closely resembles the wild and fragmenting the populations so there is less response to selection also help reduce adaptation to captivity. [ 20 ]


Solutions to minimize the factors that lead to extinction and risk of extinction often overlap because the factors themselves overlap. For example, deleterious mutations are added to populations through mutation, however the deleterious mutations conservation biologists are concerned with are ones that are brought about by inbreeding, because those are the ones that can be taken care of by reducing inbreeding. Here the techniques to reduce inbreeding also help decrease the accumulation of deleterious mutations.


These techniques have wide-ranging applications. One example is in  defining species  and subspecies of  salmonids . [ 14 ]   Hybridization  is an especially important issue in salmonids and this has wide-ranging conservation, political, social and economic implications.


More specific example, the  Cutthroat Trout . In  analysis  of its  mtDNA  and  alloenzymes ,  hybridization  between native and non-native species has been shown to be one of the major factors contributing to the decline in its populations. This has led to efforts to remove some hybridized populations so native populations could breed more readily. Cases like these impact everything from the economy of local fishermen to larger companies, such as timber.


Defining species and subspecies has conservation implication in mammals, too. For example, the  northern white rhino  and  southern white rhino  were previously mistakenly identified as the same species given their  morphological  similarities, but recent mtDNA analyses showed that the species are genetically distinct. [ 21 ]  As a result, the northern white rhino population has dwindled to near-extinction due to poaching crisis, and the prior assumption that it could freely breed with the southern population is revealed to be a misguided approach in conservation efforts.


More recent applications include using forensic genetic identification to identify species in cases of  poaching . Wildlife DNA registers are used to regulate trade of protected species, species laundering, and poaching. [ 22 ]  Conservation genetics techniques can be used alongside a variety of scientific disciplines. For example, landscape genetics has been used in conjunction with conservation genetics to identify corridors and population dispersal barriers to give insight into conservation management. [ 23 ]


New technology in conservation genetics has many implications for the future of conservation biology. At the molecular level, new technologies are advancing. Some of these techniques include the analysis of  minisatellites  and  MHC . [ 14 ]  These molecular techniques have wider effects from clarifying taxonomic relationships, as in the previous example, to determining the best individuals to reintroduce to a population for recovery by determining kinship. These effects then have consequences that reach even further. Conservation of species has implications for humans in the economic, social, and political realms. [ 14 ]  In the biological realm increased genotypic diversity has been shown to help ecosystem recovery, as seen in a community of grasses which was able to resist disturbance to grazing geese through greater genotypic diversity. [ 24 ]  Because species diversity increases ecosystem function, increasing biodiversity through new conservation genetic techniques has wider reaching effects than before.


A short list of studies a conservation geneticist may research include:


Dendrosomes [ 1 ]  are vesicular, spherical, supramolecular entities wherein the  dendrimer – nucleic acid  complex is encapsulated within a  lipophilic  shell. They possess negligible hemolytic toxicity and higher  transfection  efficiency, and they are better tolerated  in vivo  than are dendrimers. The word " Dendrosome" came from the Greek word  "Dendron" meaning tree and " some" means  vesicles . Thus dendrosomes are vesicular structures composed of dendrimers. [ 2 ]


Dendrosomes have been explored as vectors in  gene delivery [ 3 ]  and  genetic immunization .


Poly (propyleneimine) dendrosome based genetic immunization against  Hepatitis B  was found to be highly effective as compared to Dendrimer- Plasmid   DNA  complex. It has been postulated that in dendrosomes, the poly (propyleneimine) dendrimer–DNA complex is largely protected by multilamelarity of the vesicles. Moreover, it has been hypothesized that the lipoidal layers of the dendrosomes modifies the release pattern of the poly (propyleneimine) dendrimer –DNA complex, while some of the larger vesicles remain at the site of  injection  following their  degradation  by tissue  phospholipases , the smaller ones delivering and transfecting efficiently the  antigen-presenting cells  (APC) in the draining  lymph nodes . [ 4 ]  Dendrosomes have also been explored for the delivery of s10siRNA targeting E6/E7  oncogenes  in  cervical cancer . It has been reported that polyamidoamine dendrimer based dendrosomes are efficient systems for the delivery of  siRNA  for effective management of cervical cancer. [ 5 ]


Dendrosome are reported to be completely nontoxic both  in vitro  as well as  in vivo . [ 6 ] [ 7 ]


DNA encryption  is the process of hiding or perplexing genetic information by a  computational  method in order to improve  genetic privacy  in  DNA sequencing  processes. The  human genome  is complex and long, but it is very possible to interpret important, and identifying, information from smaller variabilities, rather than reading the entire genome. A whole human genome is a string of 3.2 billion base paired  nucleotides , the building blocks of life, but between individuals the  genetic variation  differs only by 0.5%, an important 0.5% that accounts for all of human diversity, the pathology of different diseases, and ancestral story. [ 1 ]  Emerging strategies incorporate different methods, such as  randomization algorithms  and  cryptographic  approaches, to  de-identify  the genetic sequence from the individual, and fundamentally, isolate only the necessary information while protecting the rest of the genome from unnecessary inquiry.  The priority now is to ascertain which methods are robust, and how policy should ensure the ongoing protection of genetic privacy.


In 2003, the  National Human Genome Research Institute  and its affiliated partners successfully sequenced the first whole human genome, a  project  that took just under $3 billion to complete. [ 2 ]  Four years later,  James Watson  – one of the co-discoverers of the structure of DNA – was able to sequence his genome for less than $1.5 million. [ 3 ]  As genetic sequencing technologies have proliferated, streamlined and become adapted to clinical means, they can now provide incredible insight into individual genetic identities at a much lower cost, with biotech competitors vying for the title of the  $1,000 genome . [ 4 ]  Genetic material can now be extracted from a person's saliva, hair, skin, blood, or other sources, sequenced, digitized, stored, and used for numerous purposes. Whenever data is digitized and stored, there is the possibility of privacy breaches. [ 5 ]  While modern  whole genome sequencing  technology has allowed for unprecedented access and understanding of the  human genome , and excitement for the potentialities of  personalized medicine , it has also generated serious conversation about the ethics and privacy risks that accompany this process of uncovering an individual's essential instructions of being: their DNA sequence.


Genetic sequencing is a pivotal component of producing scientific knowledge about disease origins, disease prevention, and developing meaningful therapeutic interventions. Much of research utilizes large-group DNA samples or aggregate genome-wide datasets to compare and identify genes associated with particular diseases or phenotypes; therefore, there is much opposition to restricting genome database accessibility and much support for fortifying such wide-scale research. For example, if an  informed consent  clause were to be enforced for all genetics research, existing genetic databases could not be reused for new studies - all datasets would either need to be destroyed at the end of every study or all participants would need to re-authorize permissions with each new study. [ 1 ]  As genetic datasets can be extrapolated to closely related family members, this adds another dimension of required consent in the research process. This fundamentally raises the question of whether or not these restrictions are necessary privacy protections or a hindrance to scientific progress.


In medicine, genetic sequencing is not only important for traditional uses, such as paternity tests, but also for facilitating ease in diagnosis and treatment. Personalized medicine has been heralded as the future of healthcare, as whole genome sequencing have provided the possibility personalizing treatment to individual expression and experience of disease. As  pharmacology  and drug development are based on population studies, current treatments are normalized to whole populations statistics, which might reduce treatment efficacy for individuals, as everyone's response to a disease and to drug therapy is uniquely bound to their genetic predispositions. Already, genetic sequencing has expedited  prognostic  counseling in  monogenic diseases  that requires rapid, differential diagnosis in  neonatal  care. [ 6 ]  However, the often blurred distinction between medical usage and research usage can complicate how privacy between these two realms are handled, as they often require different levels of consent and leverage different policy.


Even in the consumer market, people have flocked to  Ancestry.com  and  23andMe  to discover their heritage and elucidate their genotypes. As the nature of consumer transactions allows for these electronic  click wrap  models to bypass traditional forms of consent in research and healthcare, consumers may not completely comprehend the implications of having their genetic sequence digitized and stored. Furthermore, corporate privacy policies often operate outside the realm of federal jurisdiction, exposing consumers to informational risks, both in terms of their genetic privacy and their self-disclosed consumer profile, including self-disclosed family history, health status, race, ethnicity, social networks, and much more. [ 7 ]   Simply having databases invites potential privacy risks, as data storage inherently entails the possibility of data breaches and governmental solicitation of datasets.  23andMe have already received four requests from the  Federal Bureau of Investigation (FBI)  to access consumer datasets and although those requests were denied, this reveals a similar conundrum as the  FBI–Apple encryption dispute . [ 7 ]


DNA-information can be used to solve criminal cases by establishing a match between a known suspect of a particular crime and an unknown suspect of an unsolved crime. However, DNA-information on its own can lead to expected errors of a certain probability and should not be used as entirely reliable evidence on its own. [ 8 ]


As an individual's genomic sequence can reveal telling medical information about themselves, and their family members, privacy proponents believe that there should be certain protections in place to ultimately protect the privacy and identity of the user from possible discrimination by insurance companies or employers, the major concern voiced. There have been instances in which genetic discrimination has occurred, often revealing how science can be misinterpreted by non-experts. In 1970, African-Americans were denied insurance coverage or charged higher premiums because they were known carriers of sickle-cell anemia, but as carriers, they do not have any medical problems themselves, and this  carrier advantage  actually confers resistance against malaria. [ 9 ]  The legitimacy of these policies has been challenged by scientists who condemn this attitude of  genetic determinism , that  genotype  wholly determines  phenotype . Environmental factors, differential development patterns, and the field of  epigenetics  would argue  gene expression  is much more complex and genes are not a diagnosis, nor a reliable diagnosis, of an individual's medical future. [ 10 ]


Incipient legislations have manifested in response to  genetic exceptionalism , the heightened scrutiny expected of genomics research, such as the 2008  Genetic Information Nondiscrimination Act  (GINA) in the United States; however, in many cases, the scope and accountability of formal legislation is rather uncertain, as the science seems to be proceeding at a much more rapid pace than the law, and specialized ethics committees have had to fill this necessary niche. [ 1 ]  Much of the criticism targets how policy fundamentally lacks an understanding of technical issues involved in genome sequencing and fails to address how in the event of a data breach, an individual's personal genome can not be replaced, complicating privacy protection even further. [ 1 ]  As  computational genomics  is such a technical field, the translation of expert language to policy is difficult - let alone translation to laymen language -, presenting a certain barrier to public perception about the capabilities of current genomic sequencing technologies which, ultimately, makes the discourse about protecting genetic privacy without impeding scientific advancement an even more difficult one to have.


Across the world, each country has unique healthcare and research frameworks that produce different policy needs – genetic privacy policy is further complicated when considering international collaborations on genetic research or international biobanks, databases that store biological samples and DNA information.  Furthermore, research and healthcare are not the only fields that require formal jurisdiction; other areas of concern include the genetic privacy of those in the criminal justice system and those who engage with private consumer-based genomic sequencing.


91% of the largest forensic  DNA database  in the world, the National Criminal Intelligence DNA Database (NDNAD), contains DNA information from residents of  England  and  Wales . [ 8 ]  The NDNAD stores genetic information of criminally convicted individuals, those who were charged but acquitted of a recordable offence, those who were arrested but never charged with a recordable offense, and those who are under counterterrorism control. Of the 5.5 million people in the database, which represents 10% of the total population, 1.2 million have never been convicted of a crime. [ 8 ]  The  European Court of Human Rights  decided, in the case of  S and Marper v United Kingdom  (2008), that the government must present sufficient justification for differential treatment of DNA profiles of those in the criminal justice system compared to that of non-convicted individuals; essentially, there must be no abuse of retained biological materials and DNA-information. [ 8 ]  The decision highlighted several existing issues with the current system that poses privacy risks for the individuals involved: the storage of personal information with genetic information, the storage of DNA profiles with the inherent capacity to determine genetic relationships, and fundamentally, the act of storing of cellular samples and DNA profiles produces opportunities for privacy risks. As a result, the  Protection of Freedoms Act 2012  was created to ensure proper use of collected DNA materials and regulate their storage and destruction. [ 8 ]  However, many problems still persist, as samples can still be retained indefinitely in databases, regardless of whether or not the affected individual was convicted – and even the samples of juvenile delinquents. Critics have argued that this long-term retention could lead to stigmatization of affected individuals and inhibit their re-integration into society and also, are subject to misuse by discriminatory behavior innate to the criminal justice system. [ 8 ]


In 1990, the Federal Supreme Court of Germany and the  Federal Constitutional Court of Germany  decided that sections of the German Code of Criminal Procedure provided justifiable legal basis for the use of genetic fingerprinting in identifying criminals and absolving innocents. [ 8 ]  The decisions, however, lacked specific details on how biological materials can be obtained and how genetic fingerprinting can be utilized; only regulations of blood tests and physical examinations were explicitly outlined. In 1998, the  German Parliament  authorized the establishment of a national DNA database, due to mounting pressure to prevent cases of sexual abuse and homicides involving children. [ 8 ]  This decision rendered as constitutional and supported by a compelling public interest by the Federal Constitutional Court in 2001, despite some criticism that the right of informational self-determination was violated. The court did mandate that DNA information and samples must be supported by evidence that the individual can commit a similar crime in the future. To address the legal uncertainty, the Act on Forensic DNA Analysis of 2005 introduced provisions that included exact and limited legal grounds for the use of DNA based information in criminal proceedings. [ 8 ]  Some sections order that DNA samples may only be used if they are necessary to accelerate the investigation, eliminate suspects, and a court must order genetic fingerprinting. Since its implementation, there has been a monthly addition of 8000 new sets to the database, bringing into question the necessity of such wide scale data collection and whether or not the wording of the provisions provided effective privacy protection. [ 8 ]  A recent controversial decision by the German government expanded the range of familial searching by DNA dragnet to identify genetic relatives of sexual and violent perpetrators – an action that was previously deemed as having no legal basis by the Federal Supreme Court of Germany in 2012. [ 8 ]


The National Forensic Service of South Korea and the Public Prosecution Authority of South Korea established separate DNA analysis departments in 1991, despite initial public criticism that the data collection was enacted without considering the informational privacy of subjects involved, a criticism that turned to support with a series of high-profile cases. [ 8 ]  In 2006, a proposed bill by the General Assembly on the collection and operationalization of DNA information outlined crime categories for the storage, the control, and the destruction of DNA samples and DNA information. However, the bill failed to pass as it could not translate into any significant change in actual practice. The incomprehensive crime categories included were only applicable in obtaining biological information without an individual's consent, and the protocol to destroy collected samples were unclear, exposing them to misuse. [ 8 ]


The DNA Information Act of 2009 attempted to resolve these weaknesses, including provisions that stated biologically sensitive information may only be collected from convicted individuals, confined suspects, and crime scenes. Genetic fingerprinting was made permissible for specific crimes, including arson, murder, kidnapping, rape or sexual molestation, trespass upon residence at night for stealing, larceny, and burglary, and numerous other violent crimes. [ 8 ]  The act also required a written warrant for acquiring samples from convicted criminals or suspects if the concerned individuals do not give written consent. All samples must be destroyed in a timely manner if the concerned individual is proclaimed innocent, acquitted, their prosecution is dismissed, and upon their death. [ 8 ]  Importantly, if collected samples are used to ascertain individuals at the crime scene, the DNA information must be destroyed upon successful identification. However, there are still several flaws and criticisms to this legislation, in terms of clarifying the presumption of innocence, the rather trivial enforcement of sample destruction (only 2.03% of samples are deleted annually) and requisite of a written warrant (99.6% of samples are obtained without a warrant), and there is still much debate about whether or not this legislations violates the right of informational self-determination. [ 8 ]


In the United States,  biobanks  are primarily under the jurisdiction of the  Health Insurance Portability and Accountability Act (HIPAA)  Privacy Rule and the Federal Policy for Protection of Human Subjects (Common Rule). As neither of these rules was conceived with the intention of regulating biobanks and the decentralized levels of regulation, there have been many challenges in their application and enforcement, and federal law fails to directly tackle international policy and how data can be shared outside of the EU-US Safe Harbor Agreement. [ 11 ]  An area that needs clarification is how federal and state laws are differentially and specifically applied to different biobanks, researchers, or projects, a situation further complicated by the fact that most biobanks are part of larger entities, or in collaboration with other institutions, confusing the line public and private interests. About 80% of all biobanks have internal oversight boards that regulate data collection, usage, and distribution. There are three basic access models applied to the accessibility of biobank samples and data: open access (unrestricted to anyone), tiered access (some restrictions to access dependent on the nature of the project), or controlled access (tightly controlled access). [ 11 ]


GINA provisions prohibit health insurers from requiring  genetic testing  or requesting genetic information for enrollment purposes and prohibit employers from requesting genetic testing or genetic information for any type of employment assessment,(hiring, promotion, termination). However, insurers can request genetic information to determine coverage of a specific procedure. Some groups are also excluded from following GINA's provisions, including insurers and employers of federal government employees, military, and employers with fewer than 15 employees. [ 12 ]


China has a widespread network of hospitals and research institutes. It is currently undergoing a plan to create a more cohesive framework for data sharing among existing biobanks, which was previously under the jurisdiction of overlapping and confusing regulatory laws. Many biobanks operate under independently, or within a network of other networks, with the most prominent being the Shanghai Biobank network. [ 13 ]  Under this main network, guidelines detail specific de-identification policies and explicitly endorse broad consent. Recently, the Chinese Constitution has formally recognized individual privacy as a distinct and independent constitutional right, and therefore, legislators have begun developing a Draft Ordinance on Human Genetics Resources to organize national laws on biobanking management measures, legal liability, and punishment for violations. International data sharing will be even more strictly regulated under these federal laws. [ 13 ]


Biobanks in Australia are mainly under the regulation of healthcare privacy guidelines and human research ethics committees – no formal biobank legislation exists but international data sharing is widely permitted. The National Health and Medical Research Council (NHMRC) develops guidelines for and funds many of these institutions. There is discussion towards broad consent for biobanking. [ 14 ]


Electronic Frontier Foundation , a privacy advocate, found that existing legislation does not have formal jurisdiction in ensuring consumer privacy where DNA information is concerned. Genetic information stored by consumer businesses are not protected by the HIPAA; therefore, these companies can share genetic information with third parties, conditions contingent upon their own privacy statements. [ 7 ]  Most genetic testing companies only share anonymized, aggregated data with users’ consent. Ancestry.com and 23andMe do sell such data to research institutions and other organizations, and can ask for a case-by-case consent to release non-anonymized data to other parties, including employers or insurers.  23andMe even issues a warning that re-identification may take place and is possible. If a consumer explicitly refuses research use or requests for their data to be destroyed, 23andMe is still allowed to use their consumer identifying and behavioral information, such as browsing patterns and geographical location, for other marketing services. [ 7 ]


Many computational experts have developed, and are developing, more secure systems of genomics sequencing to protect the future of this field from misguided jurisdiction, wrongful application of genetics data, and above all, the genetic privacy of individuals. There are currently four major areas of genetics research in which privacy-preserving technologies are being developed for:


Paternity tests, genetic compatibility tests, and ancestry testing are all types of medical tools that rely on  string searching  and comparison algorithms. [ 1 ]  Simply, this is a needle-in-a-haystack approach, in which a dataset is searched for a matching “string”, the sequence or pattern of interest.  As these types of testing have become more common, and adapted to consumer genomic models, such as smartphone apps or trendy DNA tests, current privacy securing methods are focused on fortifying this process and protecting both healthcare and private usage.


The modern age of big data and large scale genomic testing necessitates processing systems that minimize privacy risks when releasing aggregate genomic data, which essentially means ensuring that individual data cannot be discerned within a genomic database. [ 1 ]  This  differential privacy  approach is a simple evaluation of the security of a genomic database and many researchers provide "checks" on the stringency of existing infrastructures.


One of the most important developments in the field of genomics is the capacity for read mapping, in which millions of short sequences can be aligned to a reference DNA sequence in order to process large datasets efficiently. As this high-capacity process is often divided up between public and private computing environments, there is a lot of associated risk and stages where genetic privacy is particularly vulnerable; therefore, current studies focus on how to provide secure operations within two different data domains without sacrificing efficiency and accuracy. [ 1 ]


With the advent of high throughput genomic technology allowing unprecedented access to genetic information, personalized medicine is gaining momentum as the promised future of healthcare, rendering secure genomic testing models as imperative for the progress of medicine. Particularly, concerns voice how this process will involve multiparty engagement and access to data. [ 1 ]  The distinction between genetic sequencing for medicine and research purposes is a contentious one, and furthermore, anytime healthcare is involved in a discussion, the dimension of patient privacy must be considered, as it may conflict or complement genetic privacy.


Sensitive read mapping is essential to genomics research, as read mapping is not only important for DNA sequencing, but also for identifying target regulatory molecules in  RNA-Seq . A solution proposes splitting read mapping into two tasks on a hybridized computing operation: the exact matching of reads using  keyed hash values  can be conducted on a  public cloud  and the alignment of reads can be conducted on a  private cloud . As only keyed hash values are exposed to public scrutiny, the privacy of the original sequence is preserved. [ 15 ]  However, as alignment processes tends to be high volume and work intensive, most sequencing schemes still functionally require third party computing operations, which reintroduce privacy risks in the public cloud domain.


Numerous genetic screening tests rely on string searching and have become commonplace in healthcare; therefore, the privacy of such methodologies have been an important area of development. One protocol hides the position and size of partial substrings, allowing one party (the researcher or physician) with the digitized genome and a second party (research subject or patient) with sole propriety of his or her DNA marker to conduct secure genetic tests. Only the researcher or the physician knows the conclusion of the string searching and comparison scheme and neither party can access other information, ensuring privacy preservation. [ 16 ]


The basis of personalized medicine and preventative healthcare is establishing genetic compatibility by comparing an individual's genome against known variations to estimate susceptibility to diseases, such as breast cancer or diabetes, to evaluate  pharmacogenomics , and to query biological relationships among individuals. [ 5 ]  For disease risk tests, studies have proposed a privacy preserving technique that utilizes  homomorphic encryption  and secure  integer comparison , and suggests storing and processing sensitive data in an encrypted form. To ensure privacy, the storage and processing unit (SPU) stores all the  single-nucleotide polymorphism  (SNPs) as real SNPs - the observed SNPs in the patient - with redundant content from set of potential SNPs. [ 17 ] [ 18 ]  Another solution developed three protocols to secure calculating  edit distance  using intersections of  Yao's Garbled Circuit  and a banded alignment algorithm. The major drawback of this solution is its inability of performing large scale computations while retaining accuracy. [ 19 ]


Genome-wide association studies  (GWAS) are important in locating specific variations in genome sequences that lead to disease. Privacy preserving algorithms that identify SNPs significantly associated with diseases are based on introducing random noise to aggregate statistics to protect individual privacy. [ 20 ]   In another study, the nature of  linkage disequilibrium  is utilized in selecting the most useful datasets while maximizing protection of patient privacy with injected noise; however, it may lack effective disease association capabilities. [ 21 ]  Critics of these methods note that a substantial amount of noise is required to satisfy differential privacy for a small ratio of SNPs, an impracticality in conducting efficient research. [ 5 ]


The nature of genomic sequences requires a specific encryption tool to protect against low complexity (repetitive content) attacks and KPA ( Known-plaintext attack ), given several expected symbols. Cryfa
 [ 22 ]  uses packing (reducing the storage size), a shuffling mechanism (randomizing the symbol positions), and the AES cipher ( Advanced Encryption Standard ) to securely store FASTA, FASTQ, VCF, SAM and BAM files with authenticated encryption.


Dwarfism in chickens  is an inherited condition found in  chickens  consisting of a significant delayed growth, resulting in adult individuals with a distinctive small size in comparison with normal specimens of the same breed or population.


The affected birds show no signs of dwarfism in the first weeks of age. [ 1 ]  Differences in size due to dwarfism appear slow and progressively along the growing stage. Poultry breeders begin to distinguish gradually dwarfs from normal birds by their shortest shanks and smallest body size. [ 2 ] [ 3 ]  Depending on the breed, most types of dwarfism in chickens begin to be recognized when the birds reach 8–10 weeks of age, [ 4 ] [ 5 ]  but classification is more precise when the chickens are five months old or more. At this point differences between normal and dwarf sibs is evident in all males and in 98% of the females. [ 1 ]  Dwarfs chickens reach sexual maturity and reproduce normally.


Dwarfism in chickens has been found to be controlled by several simple genetic factors. Some types are  autosomic  while others are  sex-linked , but when poultry breeders make reference to 'dwarf chickens' they  usually refer implicitly to sex-linked recessive dwarfism due to the recessive gene dw, located on the  Z chromosome .


As sex-linked dwarf  broiler  breeder hens can bring about normal sized broiler chickens, sex-linked recessive dwarfism found application in poultry industry since the last decades of the 20th century.


These hens require less food and less housing space. Their feed intake do not need to be restricted. They also have more tolerance to heat (see:  Advantages... ). So the use of sex-linked dwarf broiler female parent stocks helps to save costs and to improve animal welfare and economic efficiency in European broiler industry (see:  Use of... ). But in spite of the proven advantages of raising dwarf breeder hens, their use is not generalized in broiler industry.


Two different types of autosomal dwarfisms have been found in chickens. These types of dwarfism are controlled by genes located on the autosomal chromosomes so inherits the same way in both sexes.


In 1929 a type of dwarfism was described in different breeds of  Rhode Island Red  chickens. [ 6 ] [ 7 ] [ 8 ] [ 9 ]  This type of dwarfism produced individuals which showed a general growth delay, which was recognizable since two or three weeks of age. The outer toe was curved backwards. The skull was high and wide in relation to its length and the upper beak was curved downwards. Tongue was shortened and tumescent. Legs shortened, more in the metatarsal than in the femur. The condition was semi-lethal. None of the affected birds reached sexual maturity. It was considered as the result of a dysfunction of the thyroid gland, similar to the human pathological condition known as  myxoedema infantilis . Dwarfs of this type were homozygotes for an autosomal recessive gene  td  (thyrogenous dwarfism).


Another body size mutation was found in the experimental Cornell K-strain of chickens. Body size was reduced by about 30% and the affected birds were recognizable by 6 to 8 weeks of age. Their sexual maturity was somewhat delayed and rate of lay was about 90% that of the K-strain. Viability of the carriers was good but hatchability was poor. The condition was due to an autosomal recessive gene designed  adw . [ 5 ]


The ultimate goal of the modern genetic studies is to find out the underlying genes involved in these traits. To achieve this, the so-called positional candidate gene approach is gaining in importance. This approach is based on the genetic localization of a trait using genetic linkage analysis. Subsequent comparative mapping of the trait locus with the gene-rich maps of the human and the mouse may reveal candidate genes for the trait in question. Comparative mapping revealed that autosomal dwarfism in the chicken ( adw ) is located in a chromosomal region that is conserved between chicken, human and mouse. In the mouse the phenotype "Pygmy", similar to chicken  adw  is also located in that region. The Pygmy mouse phenotype arises from the inactivation of the High Mobility Group I-C ( HMGCI-C ). In the human the  HMGCI-C  gene is also located in the same conserved chromosomal segment.  Fluorescent in situ hybridization of chicken metaphase chromosomes using the chicken  HMGI-C  gene as a probe, showed that the chicken  HMGI-C  gene is indeed located in the region of the  adw  locus. [ 10 ]  Insulin-like growth factor 1 ( IGF1 ) is another candidate for  adw  in the chicken. [ 11 ]


In birds, female is the  heterogametic sex , that is, it has one  Z  and one  W  sexual chromosome (genotype ZW), while male (the homogametic sex) carries two  Z  chromosomes ( genotype ZZ ). Thus,  reciprocal crosses  between normal and dwarf specimens may give rather different results.


Hutt studied in the 1940s a remarkable type of dwarfism caused by only one sex-linked recessive gene to which he assigned the symbol  dw . [ 1 ]


This mutation reduces body weight in females by 26 to 32%, but the effect is still greater in homozygous males, by about 42-43%. Chicks are normal size. [ 12 ] [ 13 ]  This is the best studied type of dwarfism in chickens. Sex-linked dwarfism in meat type breeds are first recognized by the shortening of the shanks than by the lowering body weight in the rearing period [ 14 ]