A targeting vector containing (from 5' to 3') a loxP-F3-puromycin Δtk-loxP-FRT was used to disrupt Mir574 on chromosome 5. Mir574 is located in intron 1 of the host gene Fam114a1. Cre-mediated recombination removed the floxed purumycin cassette. (J:174268)