The role of the sex chromosomes in mammalian germ cell differentiation

An analysis is presented of the relationship between abnormalities of mamma- lian germ cell differentiation and their sex-chromosomal make-up. It is concluded that germ cells in an ovary require two functional X chromosomes for optimal development. The effects of X-dosage deficiency are most severe in species where there is a long period of time between the formation and utilisation of the oocytes. Thus the ovaries of XO (Turner's syndrome) and XY women are almost invariably devoid of oocytes. Germ cells in the testis on the other hand, must have only one X chromosome if they are to survive. Consequently adult XX and XXY males have sterile testes.