Males differing by the Prdm9 allele, its dosage, or background divided into classes according to fertility.

TW, mean testicular weight; SC, mean sperm count in paired caput epididymides, OFM, offspring per female per month;agenotype at Prdm9 (maternal/paternal); −, null; +, added transgenic copies of Prdm9; Background: maternal×paternal background. Note that the two fertile classes display overlapping parameters.