INS and type 1 diabetes mellitus: Concerning IDDM2 type I diabetes, it has been shown that the susceptibility locus is associated with an allelic polymorphism (VNTR) at the insulin gene (INS): the alleles having 26 to 63 repeats (class I) predispose to type I diabetes disease in the homozygous state, while the alleles having from more than 140 repeats (class III) act as a dominant protective factor against the disease.