Radiation-induced mutations at mouse hemoglobin loci.

In experiments designed to detect new mutations affecting hemoglobin, we irradiated the male or female parent in reciprocal crosses of two mouse strains that differ in alleles at the hemoglobin (Hba, Hbb) loci as well as at five other specific loci. Offspring were analyzed for hemoglobin properties (electrophoretic pattern, solubility, crystal pattern), serum albumin differences, erythrocyte lysis, reticulocyte count, and external appearance. Five hemoglobin variants were found among the mutants. In three, the genetic contribution from the irradiated father was not expressed with regard to the alpha-chain; one carried a tandem deuplication (the first known case in the mouse) involving Hbb; and one probably resulted from double nondisjunction of chromosome 7. The finding that major chromosome aberrations can mimic hemoglobin mutations indicates the need, in similar experiments, to follow F1 screening with thorough cytogenetic analysis. The variants in which there is nonexpression of the alpha chain may be the result of small deficiencies or of faults in transcription or translation. Mutation rates based on these three variants are not out of line with earlier specific-locus results, although confidence limits are still wide.