International Mammalian Genome Society

A8 Sex-of-Offspring-Specific Transmission Ratio Distortion on Mouse Chromosome X

Elena de la Casa-Esperon, Fernando Pardo-Manuel de Villena, Andrei E. Verner, Tammi L. Briscoe, Jan Michel Malette, Michelle Rosa, Wen-Hui Jin and Carmen Sapienza. Temple School of Medicine, Philadelphia, Pennsylvania

During our study of the DDK syndrome (an early embryonic lethal phenotype), we observed sex ratio distortion in favor of males in the offspring of F1 backcrosses between the C57BL/6 and DDK strains. We also observed significant and reproducible transmission ratio distortion in favor of the inheritance of DDK alleles at loci on chromosome X among female offspring but not among male offspring in (C57BL/6 x DDK)F1 x C57BL/6 and (C57BL/6-Pgk1a x DDK)F1 x C57BL/6 backcrosses. The observed transmission ratio distortion is maximum at DXMit210 in the central region of chromosome X and decreases progressively at proximal and distal loci, in a manner consistent with the predictions of a single distorted locus model. DXMit210 is closely linked to two distortion controlling loci (Dcsx1 and Dcsx2) described previously in interspecific backcrosses. Our analysis suggests that the observed female offspring-specific transmission ratio distortion is likely to be the result of the death of embryos of particular genotypic combinations, as is also thought to be the case in interspecific backcrosses.