Nonmammalian Mechanisms

Sex determination and differentiation occur in virtually all complex organisms, but the mechanisms used by various animal classes, and even by various vertebrates, differ significantly. Birds, for instance, lack a clear homolog of SRY.In birds it is the female, rather than the male, that has two different sex chromosomes, with males being ZZ, and females ZW. In many reptiles, environmental conditions, rather than genetic factors, are the primary determinant of sex. The temperature at which eggs are incubated determines sex in some lizard, turtle, and alligator species.

In both the fruit fly Drosophila melanogaster and the nematode nematode worm of the Caenorhabditis elegans, the primary sex determination mechanisms and the Nematoda pbiyluin, inany molecular cascades controlling sexual differentiation have been studied of which are parasitic

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