This allele contains exon 4 of the human TRP53 gene, with the human arginine variant at codon 72 (dbSNP:rs1042522; 72R). Codon 270, in the unmodified exon 8 - corresponding to human TRP53 codon 273 - encodes arginine (270R; mouse wild-type). A single loxP site in intron 1 is retained from an excised loxP-flanked translational STOP and selection cassette. (J:94077)