This allele is a derivative of Bcl2ltm1Mam in which the loxP flanked neomycin cassette was removed in the germline by mating mice carrying this allele to Tg(EIIa-Cre)1Lmgd mice. A single loxP site remains in place of the loxP flanked selection cassette and a second loxP site is located 3' to exon 2 in the final allele. (J:63161)