abstracts of papers presented at the 1962 meetings - Genetics

950 ABSTRACTS
protein. (Supported by grants from the American Cancer Society, The National Science Founda-
tion, and The National Institutes of Health.)
DAWSON, PETER S., University of California, Berkeley, California: Aberrant segregation ratios
in Tribolium castaneum.-Recent studies on the mapping of a sex-linked lethal (I,) in this
species of flour beetles have led to the discovery of some aberrant segregation phenomena. The
first of these involves sex ratios. A female later shown to be of the genotype +/l, produced a
progeny of three fema1es:one male (240:84) instead of the expected 2:l. Females from this
progeny were mated to several types of males with the following results: nine, 3:l ratios;
nine, 2:l ratios and eight, 1:l ratios. Females taken from the second series of 3:l ratios have
continued to segregate for all three types, while females from the 2:l series have produced
progenies of only 2:l or 1:l.-Further indication of abnormal segregation comes from two
series of matings of +r/Z2 + 9 x +r/- 3. In both cases the females used came from 3:l
progenies. From linkage tests red (r) is known to be approximately 25 units from I,. In some
matings, 2: 1 sex ratios were obtained, but the expected segregation for red did not occur. Male
offspring had higher frequencies of wild type than expected, and female off spring had higher
frequencies of red.-A final striking result was found in two sets of matings involving the
lethal and three sex-linked genes. The females used were expected to be i/z +/12, % +/f.
In all ten matings from one set and 20 from the other, the females segregated for the lethal.
Further work is in progress on all three of these phenomena.
DEFRIES, J. C., and R. W. TOUCHBERRY, University of Illinois, Urbana, Ill.: Genetic effects
of radiation on egg production of Drosophila meZanogaster.-Although important human characteristics
and most of the productive traits of domestic plants and animals are biometrical in
nature and are probably controlled by polygenic systems, little evidence is available concerning
polygenic mutations. The present report describes one of a series of studies initiated by the
authors to assess the genetic effects of radiation on biometrical traits.-Both newly emerged
males and females from Luce’s wild-type strain were subjected to various dosages of y-irradiation
(0, 500, 1000 and 1500r) and mated in all passible combinations, resulting in a four X
four factorial arrangement of treatments. Three mating pairs were included in each subclass of
two identical experiments, requiring a total of 48 mating pairs per generation. Mean daily egg
production over a ten-day period of the treated females (generation one), their progeny (generation
two), and offspring (generation three) resulting from a full-sib mating of generation
two was obtained in both experiments. Somatic effects would be expressed in generation one,
whereas genetic effects would be expressed in generations two and three. The significance of the
linear and quadratic main effects of treatment on males and females, as well as the various
interactions, were determined by orthogonal comparisons. In general, the results support previous
evidence found by the authors (TOUCHBERRY, VERLEY and DEFRIES, Genetics 47: In Press,
1962) that radiation induced polygenic damage in surviving offspring is not large. Similar data
regarding the genetic effects of radiation on other biometrical traits of Drosophila observed in
these experiments will also be presented. (This investigation was supported in part by research
grant RG-7951 from the Public Health Service.)
DE SERRES, FREDERICK J., Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tenn.:
Factors influencing wcombination and chromosome interference in Neurospora-Previous
studies (DE SERRES, Cold Spring Harbor Symposia Quant. Biol. 23:111, 1958) have shown that
both the map distances and the type of chromosome interference obtained in crosses of ad-3
mutants depended on whether strains were of identical or diverse origin. Since the ad-3 mutants
induced in unrelated wild-type strains were crossed into a 74A background, the variation observed
was attributed primarily to localized differences in the structure of homologous chromosomes.
To extend these findings, an experiment was designed to test the effect of systematic alteration
of the structure of homologous chromosomes between other linked but nonallelic markers.