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.
22.
Lepidoptera and Trichoptera ( caddisflies ) are more closely related than any other taxa, sharing many similarities that are lacking in other insect orders; for example the females of both orders are sex chromosomes, whereas in most species the males are heterogametic and the females have two identical sex chromosomes.
23.
Lepidoptera and Trichoptera ( caddisflies ) are more closely related to each other than to any other insect order, sharing many similarities that are lacking in others; for example the females of both orders are sex chromosomes, whereas in most species the males are heterogametic and the females have two identical sex chromosomes.
24.
:: 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)
25.
There has been debate on whether the MHM locus constitutes dosage compensation, however, since scientists claim that even if the MHM locus has been found to have significantly greater expression in females than in males, it could not even be considered to be a dosage compensation mechanism since it does not balance gene dose between the Z chromosome and autosomes in the heterogametic sex.
26.
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.
27.
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.
28.
Since each crossover gives 50 % recombinants, the chiasma count implies a total male genetic map length of 2450 cM . The current version of the Location Database ( Collins et al ., 1996 ) suggests a total male map length of 2851 cM . Chiasmata are more frequent in female meiosis ( exemplifying Haldane's rule that the heterogametic sex has the lower chiasma count ), and the total female map length in the Location Database is 4296 cM ( excluding the X ).
