A three-allele restriction-fragment-length polymorphism at the hypoxanthine phosphoribosyltransferase locus in man.

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Abstract
Using cloned cDNA [complementary DNA] sequences of murine and human hypoxanthine phosphoribosyltransferase (HPRT; IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8), a 3-allele restriction-fragment-length polymorphism for the restriction endonuclease BamHI at the human HPRT locus was characterized and identified. The alleles are expressed phenotypically on Southern blots as 3 distinct pairs of fragments that hybridize to HPRT cDNA: a 22-kilobase (kb)/25-kb pair; a 12-kb/25-kb pair; and a 22-kb/18-kb pair. In addition to fragments from the HPRT locus, sequences recognized by both HPRT cDNA probes are also present on at least 2 autosomes in the human genome. Allele frequencies in an unselected Caucasian population are 0.77 for the 22-kb/25-kb allele, 0.16 for the 12-kb/25-kb allele, and 0.07 for the 22-kb/18-kb allele, resulting in an average heterozygosity of 38% in females in this population. This polymorphism should facilitate gene mapping by linkage in this region of the human X chromosome.