There is no need to talk about the importance of gender. This problem is faced by doctors, livestock breeders, plant breeders. Sex genetics is one of the most important departments of the general theory of sex. The book shows that the genetics of the sex of humans, higher animals and, finally, the problem of the sex of cultivated plants are inseparable from each other in the same way as from the problem of sex in algae, fungi and protozoa.