abstracts of papers presented at the 1962 meetings - Genetics

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960 ABSTRACTS experiment using p-galactosidase formation in newly formed heteromerozygotes (PARDEE, JACOB and MONOD, J. Mol. Biol. 1:165, 1959) was consistent with the expectation that a heatsensitive repressor was present in the strain E103. Some characteristics of the heat-sensitive repressor will he discussed. HOROWITZ, N. H., HELEN MACLEOD, MARGUERITE FLING, and C. RONALD SCOTT, California Institute of Technology, Pasadena, Calif.: Tyrosinase synthesis in resting mycelium of Neuro- spora crassa.-Wild-type Neurospora makes little or no tyrosinase while growing in minimal medium, but forms the enzyme abundantly when grown under conditions of semistarvation. The enzyme is also formed on crossing media during perithecial development and is believed respon- sible for the melanization of perithecia and ascospores. Maximal synthesis of the enzyme occurs when mycelium grown in minimal medium is dissimilated in phosphate buffer at pH 6. Such cultures contain no tyrosinase initially, but after standing 48 hours in buffer, up to five percent of their extractable proteins can he accounted for as tyrosinase. The enzyme has been isolated in crystalline form from such cultures (Cold Spring Harbor Symposia Quant. Biol. 26:233, 1961). -The resting mycelial system is convenient for studying the synthesis of tyrosinase. The synthesis requires oxygen and is inhibited by divalent cations at 0.01 M, glucose, actinomycin D, and by a nucleic acid preparation from Neurospora. It is not affected by chloramphenicol or puromycin. It shows an optimum at pH 6. At pH 8.2, no tyrosinase synthesis occurs, even after the mycelium is transferred to fresh buffer at pH 6. This effect is caused by the ex- traction, at pH 8 and higher, of substances essential for synthesis of the enzyme. If the extract is adjusted to pH 6 and added back to the extracted mycelium at the same pH, enzyme production is restored. The extract can he largely replaced by a mixture containing amino acids and copper, hut such a mixture cannot account for the activity of the extract. The nature of the active material is under investigation. HOUSE, VERL L., and VIRGINIA YEATTS, Ohio State University, Columbus, Ohio: Selection for modified expression of the cubitus interruptus gem in Drosophila me1anogaster.-Eight generations of selection for increased and decreased interruption of the fourth longitudinal vein (L,) in a stock of Drosophila melanogaster homozygous for the recessive gene cubitus interruptus (ci) resulted in the formation of High and Low lines having significantly different degrees of penetrance and expressivity. Penetrance in the High line averages between 95% and 100% and has remained fairly constant from approximately the sixth generation of selection. The Low line. however, was still characterized in the ninth generation by variations in penetrance from 38% to 82% in a series of single-pair replications. Continued selection in the Low line through the 20th generation resulted in the formation of additional lines having penetrance values intermediate to those characterizing the Low and High lines. Some of these intermediate lines were unstable and give rise to stable Low lines similar to the parental Low line. The rapidity with which the original High line was established and the one-generation formation of Low lines from unstable intermediate lines suggest that the difference between the High and Low lines may involve segregation at a single major modifying locus. The truncated frequency distributions characteristic of the High and Low lines are assumed to be the result of the interruption of normal curves of vein-forming potentiality by thresholds for minimal and maximal fourth vein formation. The results for females at 26°C of interline, F, and backcross matings are compatible with the hypothesis of additive action on the transformed scale of the gene difference or differences distinguishing the two lines. HOWE, H. BRANCH, JR., Department of Bacteriology, University of Georgia, Athens, Georgia: A gene decreasing ascospore yield in Neurospora tetrasperma.-During an inbreeding experiment to develop isogenic strains, eight lines were established from random single ascospore cultures isolated from the Dodge secondarily homothallic 16387 wild-type strain. Four of the lines were selected for high fertility and four for low fertility based on ascospore yields. Twelve suc-
ABSTRACTS 961 cessive generations of single ascospore isolations were made in each line with concurrent selection maintained. Since each ascospore is usually heterokaryotic for mating type, the method provided as easy means of making repetitive intra-ascus crosses.-One of the low fertility lines showed in the fifth and successive generations a very marked decrease in the number of ascospores ejected. After 12 generations of inbreeding, the two mating types of this low yielding strain and those of a high yielding strain were isolated by conidial plating.-Tetrad and backcross analyses were made on these two high and two low yielding strains with yields being measured by spectrophotometric readings of ascospore suspensions. Strict quantitative inheritance was not found but rather a locus segregating independently of the mating type factors. This locus does not prevent production of viable progeny as do the d, E and I lethals of Dodge but instead lowers the yield, the few ascospores that are ejected being capable of germination. (Supported by Na- tional Science Foundation Grant G-13267.) Hsu, K. S., Stanford University, Stanford, California: Genetic basis of drug-resistant mutants in Neurospora.-Strains resistant to acriflavine, actidione, and caffeine have been obtained which arose by mutation of chromosomal genes. These provide a useful new class of markers in Neuro- spora.-Among the acriflavine-resistant mutants, one allele has been recovered at the acr-I locus in the left arm of linkage group I. This confers resistance to 2 pg per ml of the dye. Mutants resistant to 10 pg and 50 pg per ml have been obtained at the acr-2 locus, which is the first marker to be located in the left arm of group 111. Actidione-resistant mutants have been assigned to two loci: act-I near al-2 in IR, and act-2 in VR. All are resistant to 10 pg per ml of the anti- biotic. Resistance to 0.25% caffeine is conferred by gene caf-1 in linkage group V.-With the exception of two acriflavine-resistant mutants, which were picked up during serial subculture on acriflavine-containing minimal medium, all of the mutants were recovered by plating conidia from conidiating colonial strains (cr cot, cr cot ylo, cr rg, or cr bal) on Vogel's minimal medium plus the drug, at concentrations such that no growth was observable when 106 to 10' conidia from the sensitive strain were plated. UV-irradiation giving 50-75% killing was applied in some cases. Scoring for resistant us. sensitive is clear-cut for all of the three categories of mutants. (Supported by Public Health Service research training grant 26-158.) HUANG, P. C., S. EMERSON, and MARY R. EMERSON, California Institute of Technology, Pasadena, Calif .: Synthesis of heterokaryons involving a plasmodioid (slime) variant of Neurospora crassa, and isolation of their nuclear components.-The UV-induced plasmodioid variant, slime, of N. crassa is characterized by a Physarum-like morphology and is deficient in the cell wall. Its presumptive parent, Stanford 1207-1A, had five markers in the mating type chromosome: A, arg-2, cr, aur and os. The slime isolate retained the specific requirement for arginine and, though outcrosses to wild type were highly infertile, the five marker genes of 1207-1A segregated in the expected combinations and proportions. Three genes, os and two new mutants, are necessary but not in themselves sufficient for the production of the slime phenotype. Heterokaryons were used in the present study to detect a possible cytoplasmic factor. A heterokaryon was established between slime and Stanford strain 1413-2A carrying A, lys-3, nic-I, al-2 and OS in the mating type chromosome. Under these heterokaryotic conditions the wild-type alleles of al-2 and aur complement in the production of carotenoid pigments and those of lys-3 and nic-1 with arg-2 for growth. The inhibition of lys-3 mutants by arginine and of arg-I mutants by lysine was made use of in observations on the heterokaryons and their isolates under a variety of conditions. The results support the inference that the slime character is determined solely by the nucleus. Special techniques will be discussed and observations will be exemplified with slides. HUBBY, J. L., University of Chicago, Chicago, Illinois: Protein differences in DrosophiZa.- Analyses of ammonium sulfate fractions of the soluble protein in Drosophila have been made utilizing acrylamide gels as a supporting medium for zone electrophoresis. Several differences in migratory rates of proteins in strains of Drosophila melanogaster carrying genetic markers have
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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: ABSTRACTS 959 found in meiotic stag
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 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

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