Figure 1.

Dux KO generation, inheritance and effect on litter size. A. C57BL/6 ES cells were modified with a recombination vector that deleted the entire Dux array, and replaced it with a floxed single copy of the repeat. After removal of the selectable marker, mutant mice carrying the single floxed unit on one allele were generated by blastocyst injection. This single copy was then deleted with a germ-line cre to generate the deletion allele. B. qPCR for Dux on genomic DNA of mice of different genotypes, normalized to Dux copy number in the 1unitFL allele. The B6 WT allele is estimated to carry 22 copies of the Dux gene. C. Litter sizes of crosses between different genotypes. Data represents mean ± SEM; ^***P < 0.001. D. Genotypes of progeny from different types of crosses. The Δ/Δ genotype is underrepresented in both classes of heterozygous backcrosses.