Controlling elements in the mouse: V. Linkage tests with X-linked genes

SUMMARY Previous studies have shown that the mouse X chromosomal locus, Xce , which causes non-random X chromosome inactivation, is closely linked to the Is( X ; 7)Ct X -autosome translocation. This has placed it either near Ta on one side of the breakpoint or near jp on the other. Linkage tests with Mo vbr and Ta now demonstrate that the locus in fact lies close to Ta . The data also provide genetic evidence which establish that the C3H/HeH X chromosome carries the Xce a allele of this gene and the JU/FaCt and C57BL/GoH X chromosomes carry the Xce b allele, and further suggest that the X -linked modification of the heterozygous phenotypes of X -linked genes observed by various other investigators are all attributable to differences at the Xce locus. Evidence of a maternal influence upon Mo vbr phenotypes is also presented. This appears to operate independently of the X -inactivation process, probably through an effect of differing levels of copper in the milk in early life upon the mutant coat colour in the young.