title: Molecular and biochemical analyses of spontaneous and X-ray-induced mutants in human lymphoblastoid cells.
abstract: We have isolated a series of 14 spontaneously arising and 28 X-ray-induced mutants at the hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus in human lymphoblastoid cells. Among the spontaneous mutants, 5/14 (36%) had detectable alterations in their restriction fragment pattern after hybridization with a human cDNA probe for hgprt. Of the 10 remaining mutants, 4 had partial HGPRT enzyme activity, which suggested that they contained point mutations. Among the 28 mutants induced by 150 rad of X-rays, 15 (54%) had deletions of part or all of the hgprt gene. 5 of the remaining 13 (18% overall) had partial HGPRT enzyme activity, which suggested that they contained point mutations. These data imply that in this human cell system, X-rays induce both point mutants which have residual enzyme activity as well as mutations involving relatively large deletions of DNA.
mesh_terms: D004262:DNA Restriction Enzymes; D004351:Drug Resistance; D005796:Genes; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D008214:Lymphocytes / Q000502:physiology* / Q000528:radiation effects; D009154:Mutation / Q000528:radiation effects*; D013866:Thioguanine / Q000494:pharmacology; D014965:X-Rays
chemical_list: D007041:Hypoxanthine Phosphoribosyltransferase; D004262:DNA Restriction Enzymes; D013866:Thioguanine