On X inactivation in XO embryos of mammals

Abstract

By analogy with the situation in coccids it is suggested that in mammalian XO embryos the single X turns heterochromatic in some cells, but that such a change does not result in cell death because the X then reverts back to an euchromatic and active state. This testable alternative to the Gartler-Sparkes hypothesis would imply that the anomalies of the XO Turner syndrome are largely due to imbalance of sex-linked genes rather than developmental damage resulting from cell death and that mammalian X inactivation might become reversed in response to special developmental needs.