A CONTRAVENTION OF OHNOS LAW IN MICE

The chloride channel gene, CLCN4, has been previously mapped to the X chromosome in humans. We isolated a cDNA clone for mouse Clcn4 and use d this to map the gene in an interspecific backcross. This revealed th e surprising finding that the gene maps to the X chromosome in Mus spr etus but to chromosome 7 in C57BL/6 mice. This is the first example of a gene that contravenes Ohno's law - it is a gene unique to the X chr omosome in one eutherian species but autosomal in another. The consequ ence of this chromosomal rearrangement is that the gene is lost by men delian segregation in a subset of the male progeny of a (C57BL/6 x Mus spretus) x Mus spretus backcross.