The region of exon 10 of the endogenous mouse gene that encodes the zinc-finger array has been replaced by the sequence of the corresponding region of human PRDM9 (reference allele, variant B); coding DNA upstream of the first zinc finger and the sequences downstream of the translation stop codon are of mouse origin. Single attP and frt sites, left by FLPe excision of a selection cassette, reside upstream and downstream, respectively, of the modified exon 10. (J:228712)