what results in monosomy? -inversion, translocation, crossing-over, or nondisjunction???
103544
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.
796672
OK, draw yourself up a nice big checkerboard with 16 squares! Down the left hand side, write beside each square the 4 possible gametes produced by 1 parent - for parents with the genotypes you have given above, the gametes produced are: AB, Ab, aB, ab - this is because each egg or sperm produced will have only half the number of genes of the parent (so ONE copy instead of 2) so that when the egg and sperm meet, they will have 2 copies of each and not more!!! So the gametes will have ONE copy of the 'A' gene (which may be either the dominant 'A' allele or recessive 'a' allele - half the gametes will get one type of allele and half the other) and the same goes for the 'B' gene, to produce the possible gamete types above. Then, along the top of your little checkerboard diagram, write above each of the 4 squares the 4 possible gamete types for the SECOND parent - which in your case, are the same as the first!\n\nNow - you want to fuse your eggs and sperm to produce offspring! Do this by combining the gamete genotype of 1 parent with that of the other in the box where they meet up - eg if your very top left-hand square has the genotype 'AB' above it, and 'AB' to the left of it, then the genotype of the offspring produced will be AABB - homozygous for both! And the square 2 down from the top, in most left column, might be combining the gametes 'Ab' with AB - producing offspring AABb, which is homozygous for gene 'A' but not for gene 'B'.... and so on and so forth for the rest of the squares!\nI WOULD RECOMMEND DRAWING UP THIS SQUARE TO SHOW YOUR WORKING - YOUR TEACHER WILL BE WANTING TO SEE THAT!\ndouble homozygotes are AABB, AAbb, aaBB, or aabb...
814988
Trisomy is a form of aneuploidy where an organism has one extra chromosome in their genone (2n + 1). So a person with trisomy will have 47 chromosome (because a normal human has 46). A common example of trisomy is Down's Syndrome.\n\nThe n in 2n stands for the number of chromosomes in a haploid cell (a gamete, or 'sex cell') of that organism. So for humans it is 23 because a full set of chromosomes (2n) in a human is 46. It's more important to remember the 2n value of a species rather than the n value, which can easily be derived if you know 2n.\n\nMendel introduced the Law of Segregation and the Law of Independent Assortment using pea plants. Any half decent biology book can explain exactly what he did and how he derived these laws.\n\nCrossing over overs during metaphase of meiosis I (or metaphase I). More precisely, but probably not importantly, it actually occurs during prometaphase which is a phase between prophase and metaphase which was derived specifically to differentiate the process of crossing over from everything else which happens in metaphase. The teaching of prometaphase is inconsistent in courses so I would just stick with metaphase I for that answer.\n\nNondisjuction is when two chromosomes stay together instead of splitting up during anaphase, which results in the production of a cell with one extra chromosome and a cell with one less chromosome. This is the primary cause of Down's Syndrome which is related to maternal age, and other types of genetic diseases.\n\nMonosomy is the opposite to trisomy, that is, an organism has a genone with one less chromosome (2n - 1). It occurs just like trisomy. A human with monosomy will therefore have 45 chromosomes.
801991
Independent Assortment:\nThe chromosomes of each parent sort independently in the production of gametes, so any combination of the chromosomes is possible in the offspring.\n\nCrossing Over:\nThe swapping of segments of a chromosomes between each other.  Crossing Over creates novel combinations of alleles for various gene loci.  These combination of alleles were not present in either parent.
696673
well certain genes on the chromosomes will be transfered to different ones which means the gamits produced in meiosis will have different genes than the parent and it will be a mixed half not a normal half
62826
Caused by a terminal deletion of the most distal band of the short arm of chromosome 1, monosomy 1p36 is the most commonly observed terminal chromosomal deletion, occurring in approximately 1 in 5,000 births (Shaffer and Lupski 2000; Heilstedt et al. 2003b). As first described by the Shaffer lab in 13 subjects (Shapira et al. 1997), craniofacial characteristics of this contiguous gene deletion syndrome (CGDS)--so-called because it involves the deletion of multiple adjacent genes on the same chromosome arm--include late-closing, large anterior fontanels (membranous intervals at the intersection of the cranial bones at the crown of the skull), brachycephaly (disproportionate shortness of the head), deep-set eyes, flat nasal bridge, asymmetric ears, and pointed chin. Monosomy 1p36 is also associated with mental retardation, developmental delay, hearing impairment, seizures, growth impairment, and heart defects (Shapira et al. 1997; Slavotinek et al. 1999; Heilstedt et al. 2003a). Over 90 subjects with rearrangements of 1p36 have enrolled in our studies, of which 61 were recently published (Heilstedt et al. 2003a). The deletion sizes in the subjects vary considerably (Wu et al. 1999; Heilstedt et al. 2003a); however, there is some uniformity in the origin of the deletions, with over 60% being maternally derived (Wu et al. 1999; Heilstedt et al. 2003a). Candidate genes have been proposed for some of the individual features of monosomy 1p36, including seizures (Heilstedt et al. 2001) and facial clefting anomalies (Colmenares et al. 2002). \n\nThe Shaffer laboratory has recently identified possible mechanisms for the generation and/or stabilization of terminal deletions of 1p (Ballif et al. 2003; Ballif et al. 2004a; Ballif et al. 2004b; Gajecka et al. 2005). In addition, the Shaffer laboratory has recently demonstrated the use of microarrays--a rapid, sensitive, and high-resolution technology for the detection of many chromosomal anomalies--in the detection of deletions of 1p36 (Yu et al. 2003). \n\n\ncheck this article\n\nShapira SK, McCaskill C, Northrup H, Spikes AS, Elder FF, Sutton VR, Korenberg JR, Greenberg F, Shaffer LG (1997) Chromosome 1p36 deletions: the clinical phenotype and molecular characterization of a common newly delineated syndrome. Am J Hum Genet 61:642-650
463039
In order for crossing over to occur, two different cells are needed, one maternal and one paternal. In mitosis a cell produces two identical daughter cells (no other chromatid to cross with). In meiosis, after DNA replication the two chromatids recombined or cross over.
594069
trisomy 18 or edwards syndrome, named after john edwards who first described the syndrome in 1960, is a genetic disorder caused by the presence of three, instead of two, chromosomes 18 in a fetus or baby's cells.\n\nthus being a genetic disorder, it is inherited. but its mode of inheritance cannot be explained using the punnett square or pedigree because it is a case of trisomy, or the presence of an extra chromosome.\n\nhowever, we can show that the edwards syndrome is inherited through the non-disjunction or improper separation of chromatids 18 at meiosis.\n\nwhere:\nchromosome 18 is represented by X\nn = 23, total human chromosomes in a germ cell\n(?) is an egg cell\n<?>- is a sperm cell\n\ntherefore,\nn - 1 = 22 or without chromosome 18\nn + 1 = 24 or with additional chromosome 18\n\ndiagram production of n+1 and n-1 gametes if non-disjunction occurs at:\na. meiosis 1\n(XX) -> (XX) (_) -> (X or n+1) (X or n+1) (_ or n-1) (_ or n-1)\nb. meiosis 2\n(XX) -> (X) (X) -> (/ or n) (&#92; or n) (_ or n-1) (X or n+1)\n\nnow, using gametes from meiosis 2:\n(&#92;) + </>- = 46 or normal\n(/) + <&#92;>- = 46 or normal\n(_) + </>- = 45 without chromosome 18 (non-viable)\n(X) + <&#92;>- = 47 with extra chromosome 18 or edwards syndrome\n----------------\n2 normal : 1 non-viable : 1 with edwards syndrome\n\ntry it using gametes from meiosis 1... ;p
464570
down's syndrome is a disease that results from gaining an extra autosome through nondisjunction.  It effects autosome 21.
1184816
Are you asking about chromosome transformations such as rearrangements and translocations?
1072996
.\nThere will not be normal synapsis during zygotene of meiosis because one chromosome will not have a mate. A child may be born but the chances are that it will not be normal at all. Probably abort before birth. This is for a 47 chromosome male, and a 47 chromosome female, when the extra chromosome is an autosome.\n\nAn XXY is called a Klienfelter syndrome, sperms are usually not produced, breast development is common, voice tend to be higher pitched. The phenotype is male because of the y chromosome. Homosexuality is not mentioned.\n\nThe XXX female is sometimes fertile and can mate with a fertile XY male. There is a possibility that this female can mate with a XYY fertile male. This represents one of the few times a 47 female may mate with a 47 male and have normal children.
122042
Unless I'm mistaken, I'm afraid there are no treatments for trisomic conditions except relieving symptoms.\n\nThis is a mosaic condition, though, which means that the extra chromosome 9 is not present in all cells, so the severity of the symptoms will depend on the proportion of cells that are abnormal.
716113
There is no crossing over during prophase 2! It's a fact. That answers your question pretty nicely.
986313
T-dominant- means no tay-sachs\nt-recessive- tay sachs\n\nto have Tay Sachs you must have 2 recessive alleles so tt (this is homozygous)\nThe only way the parents could have a child with tay sachs is for both to be heterozygous for tay sachs which means Tt.\n\nYour punnent square would look like this:\n\nMom goes across and dad goes down\n\nMom-T    t\n''''''''''''_________\nD  T  I  TT I  Tt  I\nA---------------------              \nD  t  I  Tt    I  tt    I\n------------------------\n\nTo do a punnent square you write out one parent's alleles across the top and the other along the side.  Then in each box you write the alleles that are mix in each box.  You can see that the parents would produce in the first box TT which means that person is homozygous (both the same) (also since both capitols would never pass on tay sachs).   The second box across Tt which is heterozygous.  We call this person a carrier.  A carrier is someone who does NOT have tay sachs, but can give it to someone else.  The first box in the second row is Tt too.  A carrier as well.  The second box in the second row is tt.  This is homozygous again, but since a lower case t represents tay sachs this person has it.  \nSo there are 4 boxes.  1/4 of the time TT- no tay sachs\n                                     2/4 of the time Tt-carrier but no tay sachs\n                             and  1/4 of the time tt-tay sachs\n\n1 divided by 4 is .25 which is 25%.  \nThese parents have a 25% chance of having another child with Tay sachs.\n\nSorry about the punnent sq. I couldn't get it to draw right.
740184
Go back to before the child is concieved.  Back to the creation of these specific gametes.\n\nIn the meiosis process that created the gametes, one of the gametes that eventually combined to create the person ended up having an extra chromosome.\n\nInstead of the spindle fibres pulling the chromosomes apart perfectly in half ( "n" to each pole), one side of the cell got "n-1" and one got "n+1".  The gamete with "n-1" probably died from too little information, but the one with "n+1" ended up combining into the zygote and eventually became the coding for the person with Down's syndrome.\n\nDown's syndrome has an entire extra 21 chromosome.
107446
I am not sure.\nIf one X chromosome is de-activated normally perhaps the extra X chromosome in a polyploid individual is not.\nThe following link does not always open (!!!) - don't know why not. Also note it is PDF format.
692724
it is possible that half of the chromosomes in an ovum are always paternal, but that is not always the case... \n\nbecause in an organism with 56 chromosomes, even if crossing-overs are not taken in consideration, there are still 268,435,456 possible combinations of the gametes. there's a chance that all chromosomes in the ovum would be paternal. there's also a chance that all chromosomes in the ovum would be maternal. and there's also chances of any other combinations in between like more maternal than paternal chromosomes, or more paternal than maternal chromosomes, or equal numbers of paternal and maternal chromosomes.