Rac1^tm1Tyb

Targeting took place in ES cells homozyogus for the cre transgene Tg(Prm-cre)70Og, which expresses Cre recombinase only in haploid spermatids. A loxP site was introduced between exons 3 and 4 while a floxed PGK-neomycin resistance gene was introduced in reverse orientation between exons 5 and 6. Cre recombination in the male germline removed the neomycin gene, leaving exons 4 and 5 flanked by loxP sites. (J:86765)