abstracts of papers presented at the 1962 meetings - Genetics

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952 ABSTRACTS characterized by free-floating abdominal melanotic tumors (tu bw), were applied to a food surface upon which eggs were laid by nontumorous, wild-type flies, some of the eggs developed into F, adults having melanotic tumors similar in form and distribution to those of the original tumor strain. Tumorous offspring appeared with a low initial frequency of less than three per cent, but when bred together produced subsequent generations of flies with similar tumors. The proportion of tumorous flies in a given generation is quite variable, and up to 70% of flies may be tumorous after several generations of selection. In some strains the tumors appeared in early larval stages, becoming very large before or during pupation and preventing eclosion in numerous cases, Strains showing early and extreme tumor expression were inevitably lost because of lethality.-The proportion of tumorous flies in a culture tended to decrease from a first-day high to zero over a period of five days, suggesting that some essential factor, possibly an infective agent, was being either exhausted or inactivated with time. Males appear to be more susceptible to the tumors than females, and this difference persists throughout successive generations. The modes of infectivity and transmissibility of the tumor-causing agent remain obscure. A tentative hypothesis is suggested that a viral agent becomes localized in the larval gonads, and subsequently is transmitted by way of the gametes. The agent is apparently species specific, for attempts to induce tumors in D. simulans by similar techniques were unsuccessful. FLORY. W. S., and W. R. SINGLETON, Blandy Experimental Farm, Boyce, Virginia: Effects of gamma radiation on woody plants.-Nursery plants of 34 kinds of woody trees and shrubs were given a series of treatments with gamma rays (Cobalt-60) in 1958, and 23 kinds were radiated in 1959. Dosages used in 1958, ranging up to 20.000r units, were either lethal or injurious to the 15 coniferous taxa, but initially resulted in little apparent effect on any of the 19 angiospermous varieties. The much lighter dosages of 400, 800, 1200 and 1600r units were used in 1959. In 1959 there were 14 nonconiferous plants in each treatment, and numbers of surviving plants from the several dosages, after one year, were 14, 14, 12. and 12, respectively. Survivors from each lot of 32 coniferous plants in comparable treatments were 24, 22, 18, and 4, respectively. Thus with conifers, but not with woody angiosperms, the 1600r dosage resulted in a high percentage of, and even the 4.00 to 1200r treatments in considerable, lethality. In Dwarf Korean boxwood 20,000r killed the plants, while 10,000r resulted in elongated shoots. Similarly, Arnold’s Dwarf Forsythia after 20,000r produced “giant” shoots. These longer internoded shoots only appeared two and three years, respectively, following treatment.-Little is known about inheritance in woody plants, and cause for the change from the dwarf condition is uncertain. Possibilities include induction of (1) a sudden change in plants that were already periclinal chimaeras; (2) polyploid sectors; and (3) the release of restraint on a factor inhibiting internode growth and length. FOLSOME, C. E., Boston University, Boston, Mass.: Fine structure genetic analysis of recombinational topography in the phage T4 rll region.-Twenty-three sequentially arranged areas of the rII region bounded by 27 rII mutants have been located relative to four UV mutational hot spots so that some areas encompass and others do not encompass the UV mutational hot spots. UV stimulated recombination over all areas at a constant UV dose was examined. Recom- bination frequencies were elevated for all UV crosses. About UV hot spots recombination frequencies were increased by a factor of two, while at the same UV dose recombination frequencies about some UV mutationally silent areas were increased by a factor of 0.50. Other mutationally silent areas showed higher UV stimulation of recombination. No correlation was observed between map distance (0.01 to 1.00 units) and extent of UV stimulation of recombination. These results indicate that a topography of recombination in many facets reflects a topography of mutation. The results are interpreted to indicate that recombinational events at the fine structure level of analysis may originate by the same molecular mechanism as some mutational events, tautomeric shifts of nucleic acid bases.
ABSTRACTS 953 Fox, A. S., I. L. MUNYON, I. P. SINGH, and E. A. SWEENEY, Michigan State University, East Lansing, Michigan: Genetic determination, amino acid composition, and synthesis of the sez peptide of males in Drosophila me1anogaster.-The peptide characteristic of adult males has been purified by paper and column chromatography. Acid hydrolysis yields ten ninhydrinpositive products. Nine of these have been identified: a-alanine, aspartic acid, ethanolamine, glutamic acid, glycine, leucine, methionine, serine, and valine. The tenth remains unidentified. Ethanolamine must occupy what would otherwise be the C-terminal position of the peptide chain, or constitute a side branch through peptide linkage with one of the dicarboxylic amino acids or through phosphate linkage with serine. Preliminary results suggest that the unidentified residue is N-terminal.-The sex peptide first appears in males two hours after emergence. Phosphoethanolamine is present in male third instar larvae and pupae, but not in females. This disappears just prior to the appearance of the sex peptide, suggesting that it represents the source of the ethanolamine in the peptide, which is synthesized during this period.-Sex peptide is present in all 1X/2A genotypes (males) and absent in 2X/2A genotypes (females) regardless of the presence of an intact Y, or YS or YL. Females (2X/2A) transformed into intersexual males by the recessive third chromosome mutant transformer exhibit the peptide in the same concentration relative to the total free amino acid and peptide pool as do normal males. Therefore, the presence or absence of the sex peptide does not depend on the presence or absence of one or more genes, but on the balance of sex determiners and modifiers. This conclusion will be discussed in terms of regulatory mechanisms in protein synthesis. (Supported by grants from the National Institutes of Health (C-2440) and the Rackham Research Endowment.) FRYE, SARA H., 701 Atwater, Bloomington, Ind.: Concerning the X-ray dose-frequency relation for minute chromosome changes in the yellow region in Drosophila me1anogaster.-Totals of yellow mutants, X-ray-induced in y+ scute-8 chromosomes of mature and nearly mature sperm ejaculated 0-2 and %4 days after irradiation), were found to exhibit approximately a linear dose-frequency relation. The presence or absence (inactivation) of markers closely linked to yellow was determined by genetic analyses of 98% of the 558 yellows that were able to breed and were transmitted. Intergenic or “breakage” yellows accounted for 96-98% of the transmissible yellows and these were roughly classified into “only minute” and “gross” chromosome changes.-The induced frequencies of “only minutes” varied significantly below linearity with dose, whereas those of “gross changes” varied significantly above linearity. Hence, the linear dose-frequency relation of total yellow mutants is complex and consist of at least three presumptive components: sublinear, linear, and supralinear. Dose frequencies of the “only minutes” did not disagree significantly with that expected were they proportional to the 0.8 dose power. However, dose frequencies of total minutes accorded satisfactorily with the theoretical expectation of linearity if the total minutes included those gross yellows “capped” by a translocated autosomal end piece and other simultaneous gross and minute yellow changes lost by aneucentricity. Availability of a more accurate criterion of minute versus gross than the determination of which side of bb’ the right-hand break lay on would have yielded more homogeneous classes and sharper dose-frequency relations.-The dose-frequency criterion is more likely to be meaningful where heterogeneities, such as germ cell treated, structure of the mutants, and others (to be discussed) are minimal. (A.E.C. grants AT (11-1)-195 to H. J. MULLER and associates and AT (11-1)-133 to I. H. HERSKOWITZ and associates.) FUERST, R., and LI-CHUN LI, Texas Woman’s University, Denton, Texas.: Biosyntheses of pantothenate homoIogs.-WAc” and GUIRARD (1948) demonstrated that mycelium of wildtype Neurospora crassa Em5256A was able to synthesize pantothenic acid from beta alanine and pantoyl lactone.-Extending this synthesis to possible homologs of pantothenic acid, it was found that acetone-dried mycelium of wild-type and some pantothenicless mutants was able to synthesize gamma pantothenate from pantoyl lactone and gamma-amino butyric acid. Under some conditions delta pantothenate was also synthesized from delta-amino valeric acid and
Page 1 and 2: 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: ABSTRACTS 95 1 An approach to this
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 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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