PRDM9 and Infertility: To assess the impact of de novo Prdm9 alleles on these infertility phenomena, male SPRT mice were crossed with female B6 mice, heterozygous for either the humanized Prdm9 allele or for an additional engineered allele in which the DNA-binding array of Prdm9 is replaced with the orthologous sequence from the M. musculus castaneus subspecies (hereafter CAST) (Baker et al. 2014).