Regardless of their ambiguous evolutionary history, platypuses have been empirically determined to follow an XY sex-determination system, with females possessing five pairs of X chromosomes as the homogametic sex, and males possessing five X and five Y chromosomes as the heterogametic sex.
12.
:: That's not correct, since birds have no Y chromosome, and it is the male that is homogametic ( ZZ ) and the female that is heterogametic ( WZ )-the opposite of human sex determination .-Nunh-huh 19 : 59, 3 May 2007 ( UTC)
13.
One logical way to equalize gene expression amongst males and females that follow a XX / XY sex differentiation scheme would be to decrease or altogether eliminate the expression of one of the X chromosomes in an XX, or female, homogametic individual, such that both males and females then express only one X chromosome.
14.
If dioecious organisms are heterogametic and the gene locus is located on the X chromosome, it can be shown that if the allele frequencies are initially unequal in the two sexes [ " e . g " ., XX females and XY males, as in humans ], in the heterogametic sex chases in the homogametic sex of the previous generation, until an equilibrium is reached at the weighted average of the two initial frequencies.
