DNA polymorphisms, identified by an X-chromosome short-arm probe L 1.28 (DXS7), in different racial groups.

Restriction fragment length polymorphisms of the L1.28 probe which is closely linked to X-linked disorders, retinitis pigmentosa and Norrie disease, were studied in samples from England, India and Nigeria. The frequency of the A2 allele (9-kb fragment) was 0.23, 0.55 and 0.46 in England, India and Nigeria, respectively. The differences between the English and Indian populations were highly significant.