Analyses of GI tumors from Mlh1−/−;Apc1638N and Msh3−/−;Msh6−/−;Apc1638N mice revealed that both single-base substitutions and MSI induced frameshift mutations in repetitive sequences were responsible for most mutations found in the remaining wild-type (Wt) Apc allele [32],[33]. The gene discussed is APC; the disease is digestive system neoplasm.