Do you have any literature or any information on aberrant
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.
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
Click here to return to the Biology Archives
Update: June 2012