Effects of <i>Prdm9</i> alleles and dosage on reciprocal hybrids.

B6-KO, heterozygote for the Prdm9 knock-out; B6-BACB6, C57BL/6J-Tg(RP23-159N6)75Bdm male heterozygous for a Prdm9B6 transgene; Prdm9, genotype at the Prdm9 locus (maternal/paternal); −, null; +, transgenic Prdm9 alleles; n, number of males; BW, body weight (g); TW, mean weight of paired testicles in mg; SC, average sperm count (millions) in paired caput epididymides; agenotype at the entire chr17 (the rescue can also be due to a different gene, Hstw); *significantly higher than in Prdm9B6/PWD reciprocal hybrids (rows 1 and/or 3); bsignificantly higher relative testis weight (TW per body weight) compared to animals in rows 1 and 3 (p<0.002).