An EcoRI polymorphism at the insulin receptor locus on a fragment comprising exons 4 to 8.

A 593 bp EcoRI-Bgll fragment encompassing bp 1012 to 1604 of the human insulin receptor cDNA (1). Polymorphism: EcoRI detects a two allele polymorphism with bands at 10.3 and 13.5 kb (Fig. 1. Lanes 1—4 shows three homozygotes and one heterozygote). Segregation: Segregation of alleles in tumors with 19p+ marker chromosomes (2) (Fig. 1). Lane 5 shows tumor DNA with duplicated 19p+ marker chromosome and loss of normal chromosome 19. Lane 6 shows DNA from normal tissue from the same patient. Other Comments: The RFLP pattern was observed under normal hybridization and washing conditions for single copy genes.