abstracts of papers presented at the 1962 meetings - Genetics

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980 ABSTRACTS pair regularly in meiosis of the 2N hybrids, and four of the I2 bivalents are consistently heteromorphic, the differences reflecting the size of chromatic zones flanking the centromeres. The proportion of heteromorphic bivalents in the 4N hybrid meiosis can thereby provide an estimate of the extent of allosyndesis. In samples of PMC from two such hybrids, 6.6% of the bivalents were heteromorphic. Assuming random multivalent formation and a variable level of chromatid association, the yield of recessive gametes in duplex hybrids is estimated at 9.4% to 13.0%.-A genetic analysis of pairing associations can be made by testing segregation of 4N hybrids heterozygous for recessive markers derived from the esculentum parent. Testcross matings of the type a a a a x a a + + yielded from 7.4% to 15.4% (x= 10.5) multiple recessives for six markers on four different chromosomes, corresponding to the segregation expected on cytological grounds. The relatively low level of preferential pairing confirms the early findings of a close genetic relationship between L. esculentum and S. pennellii. The polyploid hybrids of these species are of more than ordinary interest for their remarkably high fertility in spite of a high level of allosyndesis. (This research was supported in part by grant G-10704 of the National Science Foun- dation.) ROBERTS, PAUL, University of Chicago, Ill.: Interchromosomal effects, crossing-over and nondisjunction in Drosophila.-Simultaneous measurements of X chromosome crossing-over and nondisjunction were made with combinations of ten different heterozygous X inversions and the Curly and Payne autosomal inversions. The percentage of X nondisjunction of the different inversions showed a statistically significant linear regression on percentage of noncrossover tetrads. Increases in crossing-over were observed with either or both autosomal inversions present but X nondisjunction rarely occurred with both Curly and Payne present. This is further evidence that the increase in crossing-over with heterologous inversions in the genome is real and not merely an artifact from elimination of noncrossovers involved in nonhomologous pairing. The latter, however, also plays a minor role under certain circumstances but occurs at a different point in meiosis.-If the older theory that chromosomes pair, cross over and disjoin is correct, a high rate of nonhomologous pairing between the X and an autosome should decrease crossing-over between the X’s. Though progeny-tested exceptional females carried only noncrossover X’s and the percentage of nonhomologous pairing in inversion-translocation bearing females was almost 50%, total crossing-over was essentially the same as in controls.-It is concluded that there are two interchromosomal effects: the primary one operating at the time of crossing-over when only homologues are paired. Subsequently, in the second effect, only noncrossover chromosomes are sufficiently affected by less specific attractive forces that they pair nonhomologously, thus dis- joining anomalously as proposed by GRFLL (1962). ROBERTSON, D. S., Iowa State University, Ames, Iowa: Suppressor and allele studies bearing on the nature of the white-albino loci of maize.-Twelve different loci of maize have been studied where mutations have resulted in carotenoid deficiencies in both the endosperm and seedling. All of these mutants have white or pale yellow endosperms and the seedlings of those with little or no measurable amounts of colored carotenoids are also devoid of chlorophyll when grown in the light and are, therefore, albino.-Suppressor studies involving the cl, locus have demonstrated that the mutant phenotype of the seedling can be suppressed either partially or completely by independent modifying genes that do not affect the phenotype of the endosperm. Allele studies at the w3, upg and y, loci have demonstrated for these mutants alleles that have phenotypes corresponding to those produced by suppressors at the cl, locus. These studies demonstrate that in some white-albino mutants, the phenotype of the seedling can be altered independently of the phenotype of the endosperm through the action of suppressors or by mutation.-The significance of these observations with respect to the structure and function of these genes is not clear. At the present time, the results can be explained at the level of gene structure by assuming a bipartite locus consisting of an endosperm and seedling component that can be affected independently by mutations and/or suppressors or at the level of gene action by assuming functional differences
ABSTRACTS 981 of the mutant alleles depending upon whether they are present in endosperm or seedling tissue. (This work was supported in part by grant G19395 from The National Science Foundation.) ROMAN, H., J. FRIIS, and N. R. EATON, University of Washington, Seattle, Washington: The effect of monochromatic ultraviolet radiation on ncciprocal and nonreciprocal recombination in yeast.-The wavelengths 248, 265, 280, and 313 mp have been used to treat a diploid yeast culture in which reciprocal and nonreciprocal recombination can be detected simultaneously. The diploid culture is heterozygous at an adenine locus and heteroallelic at an isoleucine locus. Reciprocal recombination occurring between the centromere and the adenine locus leads to sectored red-white colonies; nonreciprocal recombination at the isoleucine locus results in reversion to isoleucine independence. The shorter wavelengths are each effective in enhancing the frequency of both types of recombination to a comparable degree; A313 is ineffective. The present evidence therefore does not enable us to separate reciprocal recombination from nonreciprocal recombination spectrally. RUDKIN, G. T., DAVID A. HUNGERFORD, and PETER C. NOWELL, The Institute for Cancer Research, Philadelphia, and Department of Pathology, School of Medicine, University of Pennsylvania, Philadelphia, Pa.: DNA measurements of chromosomes, including zhe Philadelphial chromosome, in human chronic granulocytic leukemia.-Human chronic granulocytic leukemia (CGL) is characterized by a deficiency within one chromosome of group 21-22, probably number 21 (J. Natl. Cancer Inst. 27:1013, 1961). The present work is aimed at: (1) distinguishing between deletion and translocation in this abnormal karyotype, (2) the detection of possible differences in DNA content of the deficient chromosome (the Philadelphia1 chromosome, symbol Phl) in different cases of CGL, and (3) measuring the distribution of DNA within the human karyotype. Leukocytes from peripheral blood were prepared by the method of MOORHEAD, et al. (Exptl. Cell Research 20:613, 1960) on quartz slides. Following digestion of the preparations with ribonuclease, total absorbence (A,) of chromosomes at 257 mp was measured by the photographic method of CASPERSSON and SCHULTZ. Measurements have been made on one tetraploid nucleus (having two Phl chromosomes). Preliminary results show that Phl (AT=0.093) is deficient for 4.0 percent of the DNA in a group 21-29 chromosome (AT = 0.154). Were the deficient portion of the original (normal) chromosome not lost from the nucleus, but translocated to another chromosome, it should be detectable by the methods employed. Since the largest chromosome in the complement (number 1) had an A, of 0.68, the translocated piece (A, = 0.06) would add ten percent or more to any chromosome in the complement. Considering chromosome arms separately, the minimum increase due to the translocated segment would be of the order of 15 to 20%. Since the error of the method is less than ten percent, we expect to be able to distinguish between the alternatives of translocation and deletion in the CGL karyotype. RUSSELL, LIANE BRAUCH, JEAN W. BANGHAM, and CLYDE L. SAYLORS, Biology Division, Oak Ridge National Laboratory, Oak Ridge, Term.: Delimitation of chromosomal regions involved in V-type position effects from X autosome translocations in the mouse.-Two new cases of V-type position effect., both involving the c locus, have been discovered. In preliminary tests, they behave in an analogous fashion to the three reported by us earlier, and they are therefore assumed to result from X autosome translocations. One was derived from irradiation of spermatozoa; the other was spontaneous.-Further tests with the three position effects reported earlier have shown that the autosomal regions affected are limited. Translocation T(X;8), which produces b variegation, has no effect on m+. The order is tentatively assumed to be: break pokt--(7?)-W'- (6)-&(7)-m. It is doubtful whether variegation of wi (whirler) would be detectable and none has been found to date. Translocation T(X;l)c, originally detected by c variegation, also variegates p+. However, while the c regions usually occupy more than half the fur, p regions are SO small and scattered as to be almost imperceptible. The order is assumed to be: break point- (
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 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: ABSTRACTS 9 79 RBDEI, G. P., Univer
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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