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DNA polymerase beta (pol beta) cDNA of rat fused to an enhancer-promoter region plus a poly(A) signal sequence of actin 5C gene of Drosophila (abbreviated pol beta) was transferred to the Drosophila genome. Three of four constructed transgenic strains possessing transgene pol beta on different chromosomes were studied. Levels of the pol beta transcript and those of the polymerization activity of pol beta were markedly elevated in cultured cells transfected with pol beta-bearing vectors as well as in embryos of the transgenic strains. The popular idea that DNA polymerase beta participates in DNA repair was not supported by the observation that a pair of a normal and a pol beta strain, and the other pair of a mei-9 mei-41 (DNA-repair deficient double mutations) strain and a pol beta mei-9 mei-41 strain, showed no difference in survival within each pair after treatment with ultraviolet light, methylmethane sulfonate and mitomycin C. The other idea that DNA polymerase beta participates in recombination was supported by the findings that spontaneous frequency of recombination, either meiotic or mitotic, is significantly higher in a transgenic pol beta strain than in a non-transgenic strain. The enhanced recombination frequency in the pol beta strain may, however, reflect an indirect effect of over-produced pol beta proteins on chromosomal stability. Whatever the direct effect of rat pol beta is, the transgenic pol beta flies will be useful for study of the physiological role of pol beta and the mechanism of recombination.

The frequency patterns for the different kinds of dumpy mutations induced by X-rays in successive stages of spermatogenesis were studied by making two-day brood changes with 3 females per male per brood. With this mating procedure, mature sperms are probably sampled in brood A, late spermatids in brood B, early spermatids and presumably late spermatocytes in brood C, early spermatocytes in brood D.The experimental results obtained indicate that (i) the over-all frequencies of recovered complete dumpy mutations are relatively similar in broods A and B, begin to increase gradually in brood C, reach its highest level in brood D and decline sharply in brood E; (ii) the frequency patterns for the (ol, lv) and (ov, olv) exceptions over the five sampling broods are practically similar to that observed in the total dumpy mutations; (iii) no such differences in brood-mutation pattern are found, however, with respect to the yield of the (o, v) types; (iv) the over-all frequencies of recovered fractional dumpy mutations appear to be relatively steady from stage to stage, although the majority of the fractionals are of the o and v types.These findings indicate that the different kinds of dumpy exceptions may be differentially affected under different germ cell stages of maturity. Probably, this might represent a difference between point mutations and breakage events.

Mature and immature oocytes of D. melanogaster were found to show no significant difference in their sensitivity to the induction of dumpy mutations by X-rays. Genetic analysis of the recovered dumpy mutants suggested that the majority were produced without apparent breakage. Uniform sensitivity of mature and immature oocytes to X-ray-induction of point mutations may be inferred from these findings.

When male larvae carrying unstable white-zeste system were fed on a medium containing 50 and 100ppm AF-2, the incidence of somatic eye-color mutations increased approximately linearly. Since the spontaneous mutation frequency is 0.1%, the doubling dose of AF-2 is estimated at 16ppm. However, when AF-2 dose of 300ppm was given orally to adult females, the incidence of recessive visible mutations at dumpy locus and dominant visible mutations at Minute loci in primary oocytes did not increase above the control level. This indicates that the somatic mutation assay is more sensitive than the germ-cell-mutation assay, at least, after treatment with AF-2 under the conditions used.