This allele is a derivative of Amhtm5Bhr. The loxP-flanked neomycin cassette was removed by Cre-mediated recombination either by crosses with Cre-expressing mice or by in vitro transient Cre expression in ES cells prior to production of chimeric mice. This allele is a control for Amhtm2.1Bhr, Amhtm3.1Bhr and Amhtm4.1Bhr. (J:58474)