what is effect of heterochromatin?
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The pairing behavior of the sex chromosomes in male and female individuals representing seven species of Peromyscus was analyzed by electron microscopy of silver-stained zygotene and pachytene configurations. Six species possess submetacentric or metacentric X chromosomes with heterochromatic short arms. Sex-chromosome pairing in these species is initiated during early pachynema at an interstitial position on the X and Y axes. Homologous synapsis then progresses in a unidirectional fashion towards the telomeres of the X short arm and the corresponding arm of the heterochromatic Y chromosome. The distinctive pattern of synaptic initiation allowed a late-synapsing bivalent in fetal oocytes to be tentatively identified as that of the X chromosomes. In contrast to the other species, Peromyscus megalops possesses an acrocentric X chromosome and a very small Y chromosome. Sex-chromosome pairing in this species is initiated at the proximal telomeric region during late zygonema, and then proceeds interstitially towards the distal end of the Y chromosome. These observations suggest that the presence of X short-arm heterochromatin and corresponding Y heterochromatin interferes with late-zygotene alignment of the pairing initiation sites, thereby delaying XY synaptic initiation until early pachynema. The pairing initiation sites are conserved in the vicinity of the X and Y centromeres in Peromyscus, and consequently the addition of heterochromatin during sex-chromosome evolution essentially displaces these sites to an interstitial position.
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None, these are parasitic microbes and the colour of light falling on them has no effect. But if you beam un-filtered blue light which may have a substantial amount of UV lighht or UV light itself on microbes, they will die. Effect on growth will be the arresting of growth, as many genes are damaged. Efect on genes is the disruption of genes by UV light induced damage. And funnily, genes responsible for repair of UV induced damage will be switched on and will become most active genes in them during and for some time after UV light beaming.
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Hi.  I found a link to which will help you answering your question.\n\nThis is not my field of expertise, but I'm guessing the darker sections indicate heterochoramtin.  This is the portion of the chromosome that not currently being used for expression of proteins.\n\nHope this helps.  Pass on the good karma!
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It is important for hypotonic treatment.  After hypotonic treatment at room temperature, chromosomes are fixed in some fixative like methanol acetic acid fixative, and metaphase spreads are prepared.
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Mitosis is the cell division that takes place in most type of cells. In this division the entire DNA of the cell is replicated. The original cell divides into two daughter cells. Mitosis gives rise to almost all the cells in the body. \nA different type of cell division called meiosis gives rise to sperm and eggs. Here the daughter cells have only half the number of homologous chromosomes. This is because on fertilization the sperm and oveum will combine to form the zygote which will develop into the baby. Meiosis reduces the number of chromosomes by half, so in humans each sperm and each egg has only 23 chromosomes, including one chromosome from each pair of homologous chromosomes.
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During prophase 1 of meiosis, the chromosomes have duplicated and have joined with their homologous pair to form a 4 stranded tetrad.\n\nBecause you get one chromosome in each homologous pair from your mother and one from your father, although they code for the same concepts, they may code slightly differently (ie blue eyes vs brown eyes).\n\nTo exchange genetic material, during prophase one the two chromatids closest together in the tetrad (one from each mom and dad- the outer two are too far away to do this, so they remain untouched) "cross over".  Literally, the ends of the chromatids cross each other and bits of the chromosomes break off of one and reattach on the other, giving genetic variability.\n\nOk, so for example: the chromosome your mother gave you coded for blue eyes, blonde hair, curly hair, and long fingers.\nThe chromosome from your father codes for the same principles, just differently- say brown eyes, red hair, straight hair and short fingers.\n\nSo crossing over between these two occur in prophase 1, and some codes are swapped.\n\nNow we have a tetrad (4 chromatids) that code for the following.\n(We'll say the chromosome from mother is on the left and from father is on the right)\nStarting with the leftmost and going to the rightmost:\nChromatid 1 codes for: \n-blue eyes, blonde hair, curly hair, and long fingers\nChromatid 2 codes for:\n-blue eyes, brown hair, curly hair, and short fingers.\nChromatid 3 codes for:\n-brown eyes, blonde hair, straight hair, and long fingers\nChromatid 4 codes for:\n-brown eyes, brown hair, straight hair and short fingers.\n\nSo now we have the genetic variability, and 4 completely unique chromatids, that are still homologous pairs, just giving us four different codings for the same traits.\n\nHope this helps.
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The last two chromosomes decide sex.  Chromosomes carry DNA and decide in essense who we are when we start out life.  the lst chromosomes are special, they decide gender.  The egg will always carry an X.  The sperm can carry an X or a Y.  When it is XY then the baby will be male, XX is a female.  \n\nBut gender is not decided by the chromosomes in the same way that we do not simply see with our eyes.  Many sections of the brain are devoted to seeing, some people can see and now know what they see, some lack emotion responses to vision, and the like.  We are beginning to understand that what the chromosomes say do not totally influence gender.  Part of the mind decides what gender we feel, and despite what some feminists say about equality there are differences in the brains of males and females.  Horomones can have an affect on the developement in the womb as well.\n\nAnd yes it is true.  We are all females by default.  Since animals start off this way, I do wonder about Hyenas.  Er... yeah, if you know about the species than that weird comment makes sense...
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Meiosis Tutorial \nDNA replication precedes the start of meiosis I. During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. Chromosomal condensation allows these to be viewed in the microscope. Note that the bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent. The nuclear membrane disappears. One kinetochore forms per chromosome rather than one per chromatid, and the chromosomes attached to spindle fibers begin to move. Bivalents, each composed of two chromosomes (four chromatids) align at the metaphase plate. The orientation is random, with either parental homologue on a side. This means that there is a 50-50 chance for the daughter cells to get either the mother's or father's homologue for each chromosome.Chiasmata separate. Chromosomes, each with two chromatids, move to separate poles. Each of the daughter cells is now haploid (23 chromosomes), but each chromosome has two chromatids. Meiosis Tutorial \nA review of Meiosis \nComparing Meiosis and Mitosis\nChromosome behavior \nMitosis: Homologous chromosomes independent \nMeiosis: Homologous chromosomes pair forming bivalents until anaphase I \nChromosome number- reduction in meiosis \nmitosis- identical daughter cells \nmeiosis- daughter cells haploid \nGenetic identity of progeny: \nMitosis: identical daughter cells \nMeiosis: daughter cells have new assortment of parental chromosomes \nMeiosis: chromatids not identical, crossing ove \nMeiotic errors\nNondisjunction- homologues don't separate in meiosis 1 \nresults in aneuploidy \nusually embryo lethal \nTrisomy 21, exception leading to Downs syndrome \nSex chromosomes \nTurner syndrome: monosomy X \nKlinefelter syndroms: XXY \nTranslocation and deletion: transfer of a piece of one chromosome to another or loss of fragment of a chromosome. \n\nMitosis, Meiosis, and Ploidy\nMitosis can proceed independent of ploidy of cell, homologous chromosomes behave independently \nMeiosis can only proceed if the nucleus contains an even number of chromosomes (diploid, tetraploid). \nTrisomy 21 does not prevent meiosis
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So in short, sister chromatid are duplicates of the homologous pairs. I hope this helped If so 333 (I) would like the 10 points. :)\n\nThe normal chromosome number in human cells is 46. This number is called a diploid or a 2n number of chromosomes. The chromosomes consist of 23 pairs. Each pair of chromosomes is called a homologous pair. One chromosome of each homologous pair is from the male parent, and the other is from the female parent. The chromosomes of each homologous pair look alike, and they contain genes for the same traits. \n\nSister chromatids are two identical copies of a single chromosome that are connected by a centromere. \n\nFirst, consider mitosis (typical cell division) in a normal diploid cell, with two copies of each chromosome. The chromosomes are duplicated during DNA replication, and the duplicates, called sister chromatids, remain attached to one another until chromosome segregation. Each daughter cell then receives one of the sisters from each homologue pair. Importantly, this means that the daughter cells are exact copies of the mother cell, with two copies of each chromosome, so they can go through the same process again. Thus, we call this process the cell cycle.
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Chromatids are held together by centromeres.  An easy way to describe chromatids is that they are chromosomes that are stuck together.  Two chromatids are held together by a centromere, but as soon as they break apart the are now refered to as chromosomes.
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Maybe you could try to be abit more specific, but genes are information MADE of DNA, so "where" is an odd question to ask... \nMaybe you are referring to the difference between euchromatin (hypomethylated and decondensed) and heterochromatin (highly methylated and condensed) ...? If that´s the case, genes are definitely in euchromatin. That´s why heterochromatin is called "silent" DNA.
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intrinsic red cell enzyme defect.\nRed cells normally lose their nuclei and also lose their ability to produse proteins {enzymes} the conditions occures in heterozygous females
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A lot. A good one is the interaction with the anticancer drug cisplatin. It is actually platinum metal which binds to the DNA of cancer cells, inhibiting them from further multiplying. There are also silver and gold which bind to DNA and form nano-sized particles which are hot hot hot topic right now.
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try this\n\nhttp://en.wikipedia.org/wiki/Epigenetics
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Nondisjunction.  \n\nNondisjunction occurs when homologous chromosomes fail to separate during meiosis.  This results in two cell with two copies of the chromosome (when it should one have one) and two cells with none (remember that meoisis produces four haploid cells).  If the cell with the extra copy fertilizes/is fertilized by a normal haploid gamete, the result will be a trisomy.  If a cell that's missing its copy of the chromosome combines with a normal haploid cell, there result is monosomy.\n\nThe other three choices (inversion, translocation, and crossing-over) involve changes in sequence, rather than chromosome structure or number.
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A translocation of chromosome basically, means the chromosome  experienced a severe trauma of its structural integrity.  Genes may lose, mutate or turn silent or even turn on without any inhibition and therefore this will cause tremendous change to the organism.  most often, the organism will not survive but if the organism survive, the "change" you mention happended.\n\nIn humans, many syndromes are cause by translocation, even the common Down's syndrome are related to translocation of chromsome.  \n\nthis site can give a good summary:\nhttp://arbl.cvmbs.colostate.edu/hbooks/genetics/medgen/chromo/translocations.html
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Chromosomal aberrations include\n1) inversions (rearrangements of DNA segments within chromosomes)\n2) reciprocal translocations (DNA segments exchanged between chromosomes)\n3) aneuploidies (deviations from the normal diploid number of chromosomes in somatic cells, either because different chromosomes join, or there is one or more extra chromosomes, etc.)\n4) transpositions (a chromosome segment is transfered to another place in the same or a different chromosome).