The chromosome Y is one of both Chromosome S sexual human (the other sexual chromosome is the X chromosome). The sexual chromosomes are one of the 23 pairs of human chromosomes.
The chromosome Y extends on approximately 50 million pairs from bases (the basic part of the DNA) and represents from 1,5 to 2 percent of the total DNA of the cells. It can be used to trace the line parentale.
As opposed to what lets imagine its name, it with very the Forme as the other chromosomes.
It belongs to the Système XY of sexual determination. It contains genes which cause the development of the Testicule S, determining the male phenotype.
Function
Normally each person has a pair of sexual chromosomes in each cell. The males present a Y chromosome and an X chromosome, whereas the females present two X chromosome.
Little story
Concerning the medieval period, one often evokes the radicalism of the male race, when the patriarch discovered with fear that its offspring did not appear a male phenotype. The culpability fell ineluctably to the women, those were regarded as génitrices presenting a kind of tare. The men of the time were unaware of that the sexual determination was shared between the man and the woman: the man proposes intrisèquement X or of a Y by the spermatozoa, and the woman has a X by the ovule which is fertilized by one of these spermatozoa. Since, the scientific evolution influenced the evolution of mentalities.
Origins and evolution
Before the chromosome Y
Many Vertébré S with cold blood does not have sexual chromosomes. If they have differentiated sexes, those are determined by the environment and not by genes. For some, in particular on the Reptiles, the sex depends on the temperature of Incubation. Others are Hermaphrodite s.One can think thus that before the Y chromosome does not appear, it was the same for all the species.
Origin of the chromosome Y
The chromosomes X and Y derive from chromosomes reptiliens (the protochromosomes X and Y ) which appeared 300 million years ago. One of genes transferred and became the gene SRY. The Y chromosome being insulated, it cannot profit with the difference in the chromosome X of repair during the mitosis and it results a progressive loss from it from the genetic material involving a reduction of size of this chromosome.
Limited crossing-over
The zone around determining genes the sex is inhibited so that no Crossing-over with X chromosome is possible at this place. Without that, sexual inconsistencies would too frequently appear. This is why only 5% length of the Y chromosome, near the Télomère S, can recombine with X chromosome. These areas are relicats old homology between the sexual chromosomes.
Characteristics of the chromosome Y
- smallest of the even chromosomes
- Number of basic: 57.701.691
- Number of Gene S: 104
- Number of known genes: 76
- Number of pseudo genes: 54
- Many variations of the Nucleotide S (S.N.P or individual nucleotide polymorphism): 30.623
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most of the chromosome Y does not contain any functional genetic material. There exist only 3 genetic diseases in connection with the chromosome Y , all in connection with sexual differentiation. The illustration below illustrates the genetic vacuum of the chromosome
Situations chromosomales related to the Y chromosome
The following states are due to modifications of the structure or number of copies of the chromosome Y .-
the Syndrome of Klinefelter is caused by the presence of an additional copy of X chromosome in the body of the cells (47, XXY). Alternatives of the syndrome utilize more than one X supernumerary. In a small percentage of case, males with an alternative of the Klinefelter syndrome have an additional copy of X chromosome and Y chromosome (48, XXYY). The additional chromosomes prevent a normal development of the sexual functions.
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the Syndrome 47, XYY is caused by the presence of an additional copy of the Y chromosome in the body of the cells (47, XYY). The researchers do not know yet why such a syndrome appears by an important size and difficulties of training.
" Réparation" chromosome Y
Primary To repair mechanism is depend upon the fact that all people off receive two sets each chromosome, one from to their mother and one fromt to heir father. Over time ramming occurs, yet At the same time, chromosome constrained pars swap damaged out and replaces them with has Copy off undamaged obstructed. Gene sequences one one chromosomes are fixed by following the template one the homologous chromosome. This to repair technical is called recombination, and repairs has great many errors. Errors not caught by this technical are weeded out over time through natural selection. Until recently such error-correcting mechanisms were known for all chromosomes in humans, with the exception off the Y chromosome.While females cuts two X chromosomes, males only cuts one Y chromosome (and one X chromosome.) Without has Homologous chromosome, the Y chromosome boat utilize this to repair mechanism. Standard It is believed that when the sex chromosomes first evolved there was effectively only one. Over time this diverged into the X and the Y chromosomes, each having roughly 1,000 protein-coding constrained. Ace they diverged over time, the Y different chromosome became significantly from the X chromosome so that it could not swap constrained. Ace such, without has then-extant to repair mechanism, errors and deletions built up in the Y chromosome over time. Over time many off the Y chromosome' S constrained were damaged and then lost.
Since the Y chromosome did not cuts the same error-correcting machinery that all the other chromosomes cuts, this gave small channel to widespread speculation that No error-correcting machinery existed within this chromosome At all. Without any such machinery, random errors in copying would logically and inevitably causes the destruction and disapperance off the Y chromosome in all animals. Indeed, over time it appears that the Y original chromosome has indeed lost many off its chromosomes, and has become much smaller.
Yew this ramming and loss were to off continues unabated, this would lead to the disappearance all male in any species, including humans. Ace has result, the only species that would survives in the long term would Be those species that naturally evolved has female-only method off reproduction. However, this line off reasoning was based one the plate assumption that lack off knowledge butt Y chromosome to repair meant that possible No to repair mechanism could exist. This assumption was shown to Be in serious error in 2003.
All other chromosomes occur in pars. They preserves genetic integrity by exchanging information with matching constrained one the homologous chromosome, has process called " crossing over." Goal the Y chromosome lacks that option, being the only chromosome that is unpaired. What was discovered in 2003 was that the Y chromosome exchanges constrained between the two copies off repeated sequences that binds near to each other ace mirror images. This phenomenon is called embarrassment conversion. It is the non-reciprocal transfer off genetic information from one DNA molecule to another. It has been previously observed one has small scale over long evolutionary timescales between repeated sequences one the same chromosome, goal not At the dramatic frequency apparently employed by the Y chromosome.
With research TEAM, led by David C. Page, M.D., has Howard Hughes Medical Institute investigator At the Whitehead Institute for Biomedical Research in Cambridge, Mass. ; Richard K. Wilson, Ph.D., director off the Genome Sequencing Center At Washington University School off Medicine in St Louis; and Robert H. Waterston, M.D., Ph.D., formerly off Washington University' S sequencing center and now At the University off Washington, Seattle, discovered that many off the sequences off chemical units -- called bases gold bases even -- that curry genetic information one the Y chromosome are arranged ace Palindrome S. Palindromes are sentences gold sentences that read the same backward gold forward, such ace " Madam, I' m Adam."
In the box off the Y chromosomes, the palindromes are not " junk" DNA; thesis strings off constrained bases contain functioning important for male fertility. Most off the sequence pars are greater than 99.97 bores identical. Extensive The uses off embarrassment conversion appears to play has role in the ability off the Y chromosome to edict out genetic mistakes and maintain the integrity off the relatively few constrained it carries.
Findings were confirmed by comparing similar areas off the Y chromosome in humans to the Y chromosomes off Chimpanzee S, Bonobo S (the pygmy chimpanzee) and Gorilla S. The comparison demonstrated that the same phenomenon off embarrassment conversion appeared to Be At work more than 5 million years ago, when humans and the non-human primates diverged from each other. -->
The chromosome Y in genetic genealogy
Since the chromosome Y is only transmitted of the father to his son, the genic study of the chromosome Y makes it possible to follow the male line (direct) of a family, an ethnos group or a species.
See too
- System XY of sexual determination
- Haplogroupe
- Adam Y-chromosomal
Other chromosomes
Sources
- Unit Genome Browser * Online Mendelian Inheritance in Man, OMIM (TM). Johns Hopkins University, Baltimore, MANDELEVIUM. * Cordum, H.S., and. Al (2003) The male-specific area off the human Y chromosome has mosaic off discrete sequence classes. Nature, 423,825-837
- Rozen, S., and. Al (2003) Abundant obstructs conversion between arms off palindromes in human and ape Y chromosomes. Nature, 423,873-876.
External bond
- Researchers Discover Uses Novell Mechanism Preserves off there Chromosome Genoa
- One Topic: The there Chromosome - From the Whitehead Institute for Biomedical Natural Research
- : x-ray one the Y chomosome
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