fr des sexton

Dovydas
Upgrade now to see XXX rated user photos
Natalya7774
Upgrade now to see XXX rated user photos
Julia
Upgrade now to see XXX rated user photos
Andrius
Upgrade now to see XXX rated user photos
Arkadiusz87
Upgrade now to see XXX rated user photos

Xy sex determination system

The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects (Drosophila), some snakes, and some. Some fish have variants of the XY sex-determination system, as well as the regular system.

Xy sex determination system

Some fish have variants of the XY sex-determination system, as well as the regular system. The XY sex-determination system is the sex-determination system found in humans, most other mammals, some insects, some snakes, and some plants. In this system, the sex of an individual is determined by a pair of sex chromosomes.