MSH6 and neoplasm: For instance, GEMMs designed to model intestinal carcinomas driven by mismatch repair deficiency (through knockout of both Msh6 alleles) have varying phenotypes depending on the strain background: mice with a mixed background of C57BL/6J and 129S1/SvmJ produced both adenomas and carcinomas, whereas a congenic C57BL/6 mouse only produce adenomas, and the mixed background of 129/OLA and FVB/NJ rarely produced any neoplasia (121).