General Medical Information

Genetics of Ovarian Development

Joe Leigh Simpson

In the absence of a Y chromosome, the indifferent gonad develops into an ovary. Germ cells exist in 45,X human fetuses and 39,X mice; thus, presumably the pathogenesis of germ cell failure involves increased germ cell attrition, not failure of formation. If two intact X chromosomes are not present, 45,X ovarian follicles usually degenerate by birth. Therefore, the second X chromosome is responsible for ovarian maintenance rather than ovarian differentiation.

Ovarian maintenance determinants can be deduced (phenotypic-karyotypic correlations) to exist on both the X short arm and the X long arm. Each arm probably has several distinct regions of differential importance for ovarian development. The number and location will be discussed later at length. In addition to regions on the X chromosome, autosomal loci are essential for normal ovarian development.