abstracts of papers presented at the 1962 meetings - Genetics

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9 70 ABSTRACTS in a replicated experiment. Levels of relative humidity constituted the difference between environments. The high level, 70% RH, was known to increase body weight by about ten percent over the low level, 40% RH. Genetic parameters needed for predicting the direct and correlated responses from selection on either environment were estimated in the base population. While selection was based on the ability to perform in only one environment, each population was tested in the opposite environment each generation.-Good agreement between predicted and observed direct response to selection was obtained for both environments. The observed indirect responses or correlated responses to selection did not agree well with those predicted.-Heritability of the selected trait was about the same in the two environments (55-60%), yet the phenotypic variance on the low environment was nearly twice that on the high environment. These parameters plus a high positive genetic correlation for body weight on the two environments will be discussed in terms of maximum genetic improvement. (Supported by a grant from the Na- tional Science Foundation.) MEAD, C. G., Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tenn.: The relationship of a DNA-associated RNA with euchromatic and heterochromatic derived DNA of Drosophila me1anogaster.-In the process of isolating Drosophila DNA free of cytoplasmic RNA, a small fraction of RNA consistently is found associated with the DNA. The nature of this association between DNA and RNA and its relationship with euchromatic and heterochromatic derived nucleic acids has been investigated. The molar nucleotide ratio of the DNA-associated RNA is identical to that of the corresponding DNA (equating U with T) but different from that of the microsomal RNA. The ratio of the DNA to its associated RNA is found to be 2:l. The RNA is sensitive to both alkaline hydrolysis and ribonuclease digestion. A study of the rate of incorporation of P32 orthophosphate into the nucleic acids of ’third instar larvae demonstrates that the DNA-associated RNA incorporates phosphorus at a much higher rate than the microsomal RNA. Ultracentrifugal studies demonstrate a marked increase in the sedimentation ve- locity of the associated DNA after removal of the RNA with ribonuclease. The melting tem- perature (T,) of the associated DNA is increased as a result of ribonuclease digestion. These data are interpreted as evidence of a DNA-RNA complex. The RNA of this complex exhibits many of the properties of “messenger RNA.” Samples of these nucleic acid fractions derived from adult males that were coisogenic except for the presence or absence of a Y chromosome have also been examined. The DNA-associated RNA from XO and XY males exhibit molar nucleotide ratios which are identical. The major difference resulting from the addition of the Y chromosome to the genome appears to be that of a 5-10% increase in the amount of DNA as compared to the associated RNA. The simplest interpretation of the data is that heterochromatic DNA such as that derived from the Y chromosome of Drosophila does not contain an associated RNA. MEYER, HELEN U., and H. J. MULLER, Indiana University, Bloomington, Ind.: Mortality in. duced by X-irradiation of early Drosophila embryos of structurally different genotypes.-Earlier work (LAMY and MULLER 1939; MULLER and PONTFZORVO 1939-1942), utilizing offspring of triploid females, has shown that most mortality induced by X-irradiation of early embryos of Drosophila is caused by some process other than chromosome loss. We have recently reinvestigated this problem, by determining the influence of a second-chromosome deficiency (ugB) on this mortality. These experiments parallel those previously carried out in our laboratory by OSTERTAG (Thesis, 1961, and in press), and confirmed by ourselves on the influence of this deficiency on the mortality induced by X-irradiation of third-instar larvae. 8001- were delivered to embryos in the polar-cap stage (extending from blastoderm formation to beginning gastrulation). The following rates of survival to the imaginal stage were obtained for the four genotypic classes of 2536 irradiated individuals, as expressed in terms of the frequencies of survivors after irradiation relative to (divided by) the frequencies of the same classes of imagoes obtained from 1094 nonirradiated (control) embryos derived from the same crosses: structurally normal females 48.4%, deficient females 55.5%, structurally normal males 62.4%, deficient males
ABSTRACTS 971 63.1%. These results differ markedly from those obtained by OSTERTAG and by ourselves from irradiation of third-instar larvae, which show much lower mortality among females than males and among nondeficient than deficient individuals. We conclude that irradiation kills these early embryos, unlike later stages, by a different process, for the most part, than chromosome loss. Our data show, moreover, that this mortality, unlike that induced by later irradiation, is concentrated within a relatively short postirradiation period. (Supported by U. S. Public Health Service contract RG-5286, C4.) MILKMAN, R., Syracuse University, Syracuse, New York: Crossveinless polygenes in 40 wild lines of Drosophila me1anogaster.-Each of 40 wild inseminated females collected in three Syracuse locales was allowed to produce progeny. From each F, 1000 flies were examined for posterior crossvein defects. Of the 40 lines, only four contained no crossveinless (cue) flies. Among the rest, 28 contained between one and seven per 1000; five contained between 11 and 19; and three contained between 46 and 63.-The six highest strains have been subjected to selection for the crossveinless phenotype. A polygenic basis for the trait is indicated in each case, and progress has been quite rapid. These results confirm and extend conclusions about the genetic basis of the cue phenotype in nature: it appears to result from the rare combination of fairly common genes. Whether these genes in a local population are common as a class or common as individual alleles remains to be determined from crosses. Indications from crosses of cue strains of diverse origins are that for the species as a whole there are many different alleles which produce the cue trait in some teams and not in others. MITTLER, SIDNEY, and G. N. SAMPSON, Northern Illinois University, DeKalb, Illinois: Distorted sex ratio in offspring of attached-X females in D. me1anogaster.-The sex ratio of the stock B lua sCS In SSI (Muller-5) yf: = is 1 yellow forked female to 1.18 Bar eye male, however when the attached-X females are mated to Canton-S males the ratio of the offspring is 1 attached-X female to 1.98 Canton-S male. The sex ratio of the F, of this cross is 1 to 2.77. The excess of males from matings to attached-X females was also found in the offspring of matings with Oregon-R males. The F, ratio is 1 to 1.52; F,, 1 to 1.49; F,, 2,904 males to 1,974 females or 1 to 1.47. The females are always attached-X and the males Oregon-R. At first it was believed that the excess of males was due to the Y chromosomes of the Canton-S and Oregon-R in that this chromosome did not stimulate the development of the attached-X egg. The Y chromosomes that fertilize the attached-X egg in the F, and even numbered F generations are from the original M8/yf: = stock and excess males are also found in these generations. The M-5 male may not be as viable as the Oregon-R or Canton-S males and if the viability of the attached-X female is also reduced or the production of these eggs is less, this can account for the excess of males in matings to attached-X. There may be also some factor or factors on the other chromosomes introduced by mating with Oregon-R or Canton-S that may inhibit the production of attached females. MOH, C. C., Inter-American Institute of Agricultural Sciences, Turrialba, Costa Rica: The effects of p-dichlorobenzene pretreatment and temperatures on the chromosome morphology of Phaseolus vulgaris.-In studying the cytology of Phaseolus species, attempts were made to find a suitable cytological technique to facilitate chromosome counting and the morphology study. A satisfactory and relatively simple technique was to pretreat the germinating seeds (two-day old with a radicle 0.5 to 1.0 cm long) with a saturated aqueous solution of p-dichlorobenzene as described by MEYER (Stain Technol. 20: 121-125, 1945) but using low temperatures. The pretreated radicles were then excised, fixed in cold Carnoy's fluid (4°C) for two to three days, and stained with a mixture of ten parts aceto-orcein plus one part 1N HC1 before the smear was made.-Pretreatment at high temperatures (e.g. 25 "C) usually caused chromosome stickiness and little chromosome scattering, and thus made the observation difficult. The best results were obtained by pretreating the cytological material at 4°C for 6 to 24 hours depending upon the
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Page 3 and 4: ABSTRACTS 939 ARAKAKI, DAVID T., (I
Page 5 and 6: ABSTRACTS 941 BAND, H. T., and P. T
Page 7 and 8: ABSTRACTS 943 were the C57BL/6 pure
Page 9 and 10: ABSTRACTS 945 BROWN, RUSSELL V., an
Page 11 and 12: ABSTRACTS 94 7 development of corn
Page 13 and 14: ABSTRACTS 949 some closely linked t
Page 15 and 16: ABSTRACTS 95 1 An approach to this
Page 17 and 18: ABSTRACTS 953 Fox, A. S., I. L. MUN
Page 19 and 20: ABSTRACTS 955 mutants which form a
Page 21 and 22: ABSTRACTS 95 7 tion, respectively,
Page 23 and 24: ABSTRACTS 959 found in meiotic stag
Page 25 and 26: ABSTRACTS 961 cessive generations o
Page 27 and 28: ABSTRACTS 963 tances. For genes mor
Page 29 and 30: ABSTRACTS 965 environment interrela
Page 31 and 32: ABSTRACTS 967 dent maize inbred lin
Page 33: ABSTRACTS 969 procedure leaves much
Page 37 and 38: ABSTRACTS 973 hours to several week
Page 39 and 40: ABSTRACTS 975 to mutagen-induced li
Page 41 and 42: ABSTRACTS 977 the course of the exp
Page 43 and 44: ABSTRACTS 9 79 RBDEI, G. P., Univer
Page 45 and 46: ABSTRACTS 981 of the mutant alleles
Page 47 and 48: ABSTRACTS 983 enzyme synthesis.-Fiv
Page 49 and 50: ABSTRACTS 985 infected. Because vir
Page 51 and 52: ABSTRACTS 987 +/Su-V and Su-V/Su-V
Page 53 and 54: ABSTRACTS 989 sulfate concentration
Page 55 and 56: ABSTRACTS 991 XI1I.-These observati
Page 57 and 58: ABSTRACTS 993 body” is observed i
Page 59 and 60: ABSTRACTS 995 possibly third) mitot
Page 61: ABSTRACTS 997 indole requirement si

abstracts of papers presented at the 1962 meetings - Genetics

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