abstracts of papers presented at the 1962 meetings - Genetics

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990 ABSTRACTS Four lines of genetically isolated turkeys (one random-bred, and three experimentals, each selected for a single trait), six generations removed from a common base population, have demonstrable differences for several blood factors. When tested at Serology Laboratory, Uni- versity of California, Davis, lines 3 and 4 (selected for egg production and hatchability, respectively) were found to be devoid of factor Q, common in lines 1 and 2 (random-bred and large-body size, respectively). Tests at WSU have revealed quantitative differences between lines 1 or 2 and lines 3 or 4 for F and M antigenic complexes: there is relatively more M and less F in lines 1 and 2 than in lines 3 and 4. When antiturkey rabbit serum B, produced by injecting RBC from 2 to 4 month old turkeys (I), was, first, incompletely absorbed with RBC of (1) or of 10 to 12 month old turkeys (2), differences in RBC “absorption power” were revealed: RBC of (2) showed lower values. Reverse was true for antiturkey rabbit serum W, obtained by injecting (2) RBC and then partially absorbing the serum with (1) or (2) RBC. A tentative explanation, supported by other related observations at this laboratory, is that (2) RBC carry more M antigens and less F than (1 ) RBC. Thus, lines 1 and 2 are antigenically closer to (2)-type RBC and lines 3 and 4 to (1)-type RBC. (Project 1600, supported, in part, by funds provided for biological and medical research under State of Washington Initiative No. 171.) TANO, S., and A. B. BURDICK, Purdue University, Lafayette, Ind.: Female fecundity of Drosophila melanogaster second chromosome recessive lethal heterozygotes in homozygous and heterozygous genetic background.-Eighteen spontaneous lethals were introduced separately to homozygous S-2 genetic background by a system which allowed an average of 13.7% residual heterozygosity from the original lethal stock, i.e., a section averaging 39.4 crossover units surrounding the lethal remained unsubstituted by S-2. Fifty l/+ females, divided into five replications, were observed for egg production during the third through sixth days after eclosion. Heterozygous background was produced by crossing the S-2 background strains with W-109, an unrelated homozygote.-In homozygous background where the female fecundity (f) of S-2 is taken at 1.000, the mean f of the 18 lethal heterozygotes was 1.475, all values being greater than 1.19. When the f values were corrected for the 13.7% residual heterozygosity, the mean f became 1.280 and only one of the 18 values fell below 1.0. Five of the corrected f values were considered to be significantly greater than 1.000, while the group as a whole could be considered to represent samples drawn from a population the over-all mean of which was greater than 1.000 since 17 of the 18 values fell above 1.000.-1n heterozygous background, where the hybrid S-2/w-109 was taken as 1.000, the mean f value was 0.961, all values being less than 1.05, 11 of them less than 1.000. There was no rank order correlation between f values obtained from homozygous and heterozygous background.-Larval, or preadult, viability has been the usual means of estimating the consequences of heterozygosity for deleterious genes, whereas f is equally important in over-all fitness. The present study indicates that the f consequences are relative to the degree of heterozygosity of the genetic background. (Supported by NIH E-1428.) TAUB, STEPHAN R., Harvard University, Cambridge, Mass.: The effect of nuclear genes on nuclear differentiation in syngen 7, Paramecium aure1ia.-A mutant strain (m7-1) restricted to mating type XI11 arose following ultraviolet irradiation of type XIV cells of a wild-type strain (d7-1) capable of expressing either mating type XI11 or XIV. In the progeny of hybrids formed between the mutant and wild-type strains the restriction to type XI11 is observed to segregate in a 1 : 1 ratio from the ability to express either type. Thus a mutation at a single locus is sufficient to account for the origin of m7-1. The mutant gene at this locus is designated n, its wild-type allele, N. The progeny of crosses of heterozygotes (N/n) on mating type XIV to stock 38, strain homozygous for mtxl11, a gene which, like n, restricts homozygotes to type XIII, are capable of expressing either type XI11 or XIV. Breeding analyses of these progeny reveal that the N and mt loci are unlinked.-As is the case with homozygotes for mtXIII (TAUB, Genetics 44:541, 1959), progeny genically competent to express either mating type which derive their cytoplasm from stock m7-1 (n/n) become type XIV. However, in contrast to the case at the mt locus, genically competent cytoplasmic progeny of heterozygotes of type XI11 become
ABSTRACTS 991 XI1I.-These observations can be explained by a hypothesis which assumes that: (1) the mt and N loci control separate steps in a sequence which results in the production of the XIV mating type substance; (2) the ability of the macronucleus to differentiate to control only one of two alternative mating type potentialities reflects the ability of the wild-type allele at the mt locus (or, less likely, at the N locus) to be repressed when differentiation occurs in the presence of a hypothetical substance, “R’; (3) “R” is a precursor of the XIV mating type substance. (Sup- ported by a grant from the Natisonal Science Foundation.) THOMPSON, PETER E., Iowa State University, Ames, Iowa: Synaptic modification of dominant lethal frequencies after irradiation of the Drosophila testis.-Increases in the mutability of unpaired chromosomes have led to the interpretation (THOMPSON, Genetics 47:337, 1962) that the synapsis of homologous chromosomes is a major factor in the repair of radiation induced chromosomal damage. This hypothesis is subtantiated by the present data on the production of dominant lethals among males in which complex structural heterozygosity (presence of multiple inversion SM5) has created almost total asynapsis of one major pair of chromosomes. Egg development among one-day broods from such males after X-ray treatment gave evidence of an appreciable increase in dominant lethals of meiotic origin, in comparison with males lacking structural heterozygosity.-The brood pattern of dominant lethals from irradiated control males shows a plateau of maximum frequency from early meiosis to spermatid stages, i.e., among sperm sampled from the fifth to the eighth day after irradiation. Broods from irradiated SM5 males gave similar frequencies for premeiotic and postmeiotic stages, including the fifth and tenth brood periods, but during days 6-8 about twice as many dominant lethals were scored among these lines. If dominant lethals may be equated with highly aberrant rearrangement or loss of chromosome fragments, asynapsis appears to contribute markedly to gross genetic damage during meiosis. (Supported by Grant RG-8912 from the National Institutes of Health.) TUVESON, R. W., Department of Botany, University of Chicago, Chicago 37, Illinois: Hyphal tip isolation as a criterion for heterocaryosis.-Specific heterocaryons between auxotrophic strains of Cephalosporium mycophilum exhibit selection for the incorporation of one of the nuclear types into the conidia produced by the heterocaryon. Growing the specific heterocaryons on supplemented minimal medium resulted in altered nuclear proportions and recovery of the minor nuclear component. Hyphal tip isolations from one of the heterocaryons exhibiting selection when grown on minimal medium were incapable of continued growth on minimal medium although tips transferred to complex medium grew vigorously. These results suggested that the hyphal tips were homocaryotic for the dominant nuclear component. However, the heterocaryotic nature of the mycelium had been previously established by the isolation of a somatic diploid from which recombinants were subsequently recovered. Manipulating concentrations of supplements in the minimal medium on which the heterocaryon was grown has resulted in the isolation of hyphal tips able bo grow on minimal medium. Supplementation of the medium presumably altered nuclear proportions, thus allowing for the isolation of hyphal tips capable of growth on minimal medium. In species of Fusarium, isolation of hyphal tips from specific hetercaryons exhibiting selective incorporation of nuclear types into conidia revealed that a high proportion of these tips were capable of continued growth on minimal medium. These results suggest that selection was not severe enough in these heterocaryons to preclude the isolation of heterocaryotic hyphal tips. These experiments indicate that the inability to isolate hyphal tips capable of continued growth on minimal is not conclusive evidence against heterocaryosis, but may reflect severe selection resulting in a high proportion of homocaryotic tips. The results with Fusarium indicate that selective incorporation of nuclei into conidia need not result in homocaryotic tips. UNDERKOFLER, JUDITH, and M. R. IRWIN, University of Wisconsin, Madison, Wisconsin: Inieraction products of new combinations of genes in species crosses of Co1umbidae.-A hybrid substance is defined as an antigenic product of the erythrocytes of an individual (species hybrid
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ABSTRACTS OF PAPERS PRESENTED AT TH
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 and 34: ABSTRACTS 969 procedure leaves much
Page 35 and 36: ABSTRACTS 971 63.1%. These results
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: ABSTRACTS 989 sulfate concentration
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
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abstracts of papers presented at the 1962 meetings - Genetics

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