This allele is a derivative of Apctm2Rak in which the loxP-flanked exon 14 sequences have been deleted by Cre-mediated recombination in the germline. A single loxP site remains in place of exon 14 and flanking intronic sequences. Loss of exon 14 is predicted to introduce a frameshift mutation and a premature stop codon, resulting in a truncated protein.