Molecular characterization of 15 rearrangements among 90 human in vivo somatic mutants shows that deletions predominate.

Ninety hypoxanthine phosphoribosyltransferase-deficient mutants were isolated from lymphocytes of 31 individuals drawn from both control populations and populations exposed to low doses of ionizing radiation. Southern analysis of the DNA revealed altered hybridization patterns in 15 mutants. Of these, 14 changes consisted of deletions of 2 to 40 kilobases or more.