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Question:
Do you have any literature or any information on aberrant Y-Chromosomes? I am doing research on this for forensic purposes. I have only heard of one case in which the individual was a male, however only displayed the X-Chromosome when typed (Amelogenin). Any help would be appreciated.



Replies:
Since the X and Y are not considered to be homologous (identical) because the X contains so much more info. than the Y. The Y really only contains the info. necessary to make a boy. Autosomal chromosomes (non-sex) are homologous. They contain the same information in the same order, although they may have different versions of the traits ( ie. they both contain genes for eye color but one has the blue version and the other has the brown version). During prophase I of meiosis, crossing over of homologous chromosomes occurs where they exchange pieces. The X and Y, not being homologous don't usually crossover. However, there have been found to be small regions of the X and Y that do have genes in common. This is called the pseudoautosomal region and has been known to be involved in crossing over. I have heard of very rare cases where the SRY gene (the "maleness" gene) has been found to have crossed over to the X chromosome. The karyotype would show the sex to be XX, or female, but one of the X's contains the SRY gene and causes the male pattern of development.

K. Van Hoeck



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