Restriction fragment length polymorphism of the human insulin receptor gene among Mexican Americans.

Recently, we examined a restriction fragment length polymorphism (RFLP) at the insulin receptor locus in Mexican Americans. This RFLP can be detected using the restriction endonuclease Rsa I, and has three alleles of 3.4 kb, 6.2 kb, and 6.7 kb. Our data suggested that the 3.4 kilobase pair (kb) allele may be associated with type II (non-insulin dependent) diabetes mellitus in Mexican Americans. We initiated studies to identify additional polymorphisms at the insulin receptor locus that might be useful in further studies on the association of type II diabetes and the insulin receptor gene. During the course of these studies we observed that the 6.7 kb and 6.2 kb alleles of the RsaI polymorphism appears to be due to an insertion or deletion of DNA sequences, so that DNA fragments of different lengths are generated when DNA from heterozygous individuals is digested with selected restriction endonucleases that cut on either side of this region. The 3.4 kb allele is apparently due to a site specific polymorphism. In the present report, results of these findings are presented as well as a description of additional polymorphisms that we have identified among Mexican Americans.