X-Linked Hypoxanthine-Guanine Phosphoribosyl Transferase Deficiency: Heterozygote Has Two Clonal Populations

Abstract
Clones of skin fibroblasts cultured from the mother of two sons with X-linked hypoxanthine-guanine phosphoribosyl transferase deficiency (Lesch-Nyhan syndrome) were assayed for activity of this enzyme by measurement of the incorporation of 3H-guanine into guanylic acid as counts per minute per microgram of protein and by autoradiography. The demonstration of two populations of clones, wild-type clones with normal enzyme activity and mutant clones unable to incorporate 3H-guanine, is evidence that the locus for hypoxanthineguanine phosphoribosyl transferase on one of the X chromosomes is inactive.