Controlling elements in the mouseX-chromosome: I. Interaction with the X-linked genes

Abstract

The mouseX-chromosome controlling elements, detected by their influence on the position effect variegation caused by theX-autosome translocationT(1;X)Ct, have been found to modify the heterozygous phenotypes of twoX-linked genes. It is proposed thatX-inactivation can be incomplete, the level of inactivation or the frequency of cells in which inactivation is incomplete being dependent upon the ‘state’ of the controlling element located in theX. The data suggest that this is a consequence of a reversal, or partial reversal, of inactivation of theXas a whole in some cells rather than a vairable spread of inactivation along the length of theX.