Abstracts of Papers Presented at the 1962 Meetings of the Genetics Society of America

1962 Genetics  
Glucose metabolism in PHH and PHL strains of Mus musculus.-Oxidation of glucose to CO, by male PHH and PHL mice was measured continuously by use of a Roth metabolism chamber and flow ion-chamber electrometer. Each mouse was injected by heart puncture with glucose 1-, 2-, 6-, U-Cl4, or lactate 1-Cl4, at one, five, or nine hours after onset of the controlled light period. -From earlier 24 hour gravimetric tests, both strains produced 5.8 ? 0.12 mg of CO,/gram/ animal/hour.-Maximum C140,
more » ... occurred ten to 40 minutes following injection. Approximately U) percent of the CO, from glucose was derived from C-2 and 12 percent from each of C-l and C-6. Urinary radioactivity was negligible. The glucose l-C14:glucose 6-C14 ratio approximates unity in both strains, suggesting that glucose is oxidized as a symmetrical molecule. Essentially all combusted blood glucose can be accounted for by glycolysis and subsequent TCA cycle activity. Considering only data obtained from mice injected at the midday period, PHL males seem better equipped to oxidize glucose to CO,. However, study of strain-time of daysubstrate interactions suggest that mice differ in their peaks of metabolic activity and that strain comparisons have meaning only when measured at several different times in a 24 hour period. lands: Nonpreferential pairing of translocated chromosomes in tetraploid rye.-The diploid translocation heterozygotes of Secale cereale L. obtained by crossing cytologically normal summer ( ? ) x winter homozygous for a large-sized reciprocal translocation had summer growth habit. The colchicine induced tetrapliods of these heterozygotes showed a strong tendency for nonpreferential pairing of translocated chromosomes. Whereas the normal chromosomes associated in bivalents, trivalents and quadrivalents, the translocation complex formed multivalents up to octavalent, present as rings and chains at metaphase I. All the latter multivalent associations were characterized by their heteromorphic nature. The degree of nonpreferential pairing as indicated by the percentage of the chromosomes involved in multivalents was far higher for the interchanged chromosomes (72%) than that for the normal (38%). Abnormal chromosome segregation leading to hypoploid and hyperploid diads and tetrads, univalent laggards which divided precociously, and bridges were observed at anaphase I and 11. A high percentage of the microspores showed univalents and micronuclei in their cytoplasm.-In view of the hypotheses by other authors that the S. cereale genome originated through stabilization of translocated chromosomes, it is conceivable that such a raw genome would survive better at a diploid than a polyploid level. One reason for the absence of polyploidy in the genus Secale as against its widespread occurrence in the related grass genera may thus be accounted on the basis of nonpreferential pairing of the translocated chromosomes. Ribonucleic acid in heterochromatin.-Cytologically well-defined heterochromatic regions, such as the "prochromosomes" of the interphase nucleus of the spring-flowering Scilla sibirica, were analyzed cytochemically for RNA content by enzymatic hydrolysis, and by autoradiography following incorporation of tritiated RNA precursors. Results of hydrolysis of fixed cells with ribonuclease alone, deoxyribonuclease alone, or consecutive treatments with both nucleases, followed by staining with methyl green-pyronin or azure B, show that RNA is present in heterochromatin. The results also suggzst that there may be two RNA components in the heterochromatic regions: one that is labile and more easily digested; and a second, more resistant, which may be complexed with DNA since it requires pretreatment with deoxyribonuclease to render ABSTRACTS it easily hydrolyzable by ribonuclease.-Autoradiography of Scilla root-tip cells into which RNA precursors (H3-cytidine or H3-uridine) had been incorporated confirmed the presence of RNA in the heterochromatic "prochromosomes." After digestion of the fixed tissue with deoxyribonuclease, the autoradiographs showed a heavy concentration of silver grains over the "prochromosomes." This radioactivity was eliminated by ribonuclease treatment. It appears that, in Scilla, H3-cytidine is initially incorporated into RNA exclusively for a very long period of time, since the label first appears in DNA after eight or ten hours. The possibility is discussed that the length of this period reflects the state of the nucleotide pool and is dependent on the presence of many heterochromatic bodies. (Supported in part by a National Science Foundation Cooperative Graduate Fellowship and by USPHS research grant RG-149.) ALLEN, SALLY LYMAN, and MARGARET SEGUR MISCH, University of Michigan, Ann Arbor, Mich.: Genetic and epigenetic factors affecting the acid phosphatases of Tetrahymena.-Among the family of acid phosphatases separated electrophoretically in starch gels, alternative forms of one of these enzymes occur within inbred strains of variety 1 of Tetrahymena pyriformis. A single zone (P-1A) appears in strains A, AI, B1, D and D I ; a group of two to three zones with more basic charge (P-1B) appears in strains B, C, E and F. Within a strain, each type breeds true. The hybrid (P-1AB) possesses a hybrid as well as parental enzymes. Genetic analysis indi- cates that these phosphatases are controlled by alleles at a single locus. A cross of A x B resulted in 18 P-IAB pairs. When intercrossed, the hybrids gave rise to 11 A, 19 AB and ten B pairs; backcrossed to A, to ten A and ten AB pairs; backcrossed to B, to eight B and 12 AB pairs. The progeny of all crosses were screened immediately following conjugation. At this time the enzymatic patterns of heterozygotes from all crosses were similar, if not identical. However, the patterns of F1 P-1AB caryonides at 150 fissions showed marked variation. Variations now occurred at five electrophoretic positions. Subclonal analyses of selected caryonides showed a strong hereditary influence within a clone in pattern. Some caryonides were P-1A or P-lB, the frequency (14%) being lower than that (58%) of caryonides with parental H serotypes. The higher frequency is expected as a consequence of subnuclear differentiation and random segregation of subnuclei. The lower frequency, if repeatable, might arise if other genetic factors interacted with the P-l alleles to stabilize the hybrid condition of the subnuclei. (Supported by grant C-3545 from the National Cancer Institute, USPHS.) ALTENBURG, EDGAR, and LUOLIN S. BROWNING, Texas Medical Center, Inc., Houston, Texas: Evidence for the duplicational origin of reverse mutations at the forked locus in Drosophila. -Among approximately 490,000 offspring of f3"+ females (nonforked) derived by reverse mutation from f 3 w (a forked allele) in Drosophila, 30 spontaneous mutations occurred back to forked (of varied phenotypes), or about one forked mutation in 16,300 chromosomes. This relatively high mutation rate of the reverted allele (i.e., of f 3 H + to f 3 9 is comparable to that of f 3 N to f38+ in diploid material as found by us (38 in approximately 400,000, or about one in 10,600) and previously reported by G. LEFEVRE and M. GREEN. There is also a high rate of mosaicism among f3y+ flies; 34 forked mosaics were found among the above 490,000 offspring, or about one mosaic in 14,400. These observations suggest that the above mutations might be duplications and deleletions within the forked locus. The reverse mutations (of fjv to f " + ) would result from duplication of the right subsegment of the forked locus. The duplication will be a suppressor of f3N, which is located in the left subsegment. I t would occur at early prophase in a mitotic division (of a gonia1 cell in the case of the germ track) and would result from one split X receiving both right segments of the forked locus, and the other neither. Mutations of f3p+ to f"" would result from deletion of one or both elements of the duplicated right segment. In the case of the mosaics, deletion would have occurred in a somatic cell during development. The suppressor of forked ( f + i h ) which arose at the same time as a forked deletion ( f " ) , as earlier reported by MULLER and OSTER could also be interpreted as a duplication of the right segment of the forked locus. ABSTRACTS 939 ARAKAKI, DAVID T., (Introduced by JIMMIE B. SMITH), Genetics Department, University of Hawaii, Honolulu 14, Hawaii: Chromosomal analysis of normal and mongoloid individuals of uarious ethnic groups in Hawmi.-The chromosomal patterns of 32 normal persons were examined by the leukocyte culture technique. Normal samples represented seven different ethnic groups: Japanese, Chinese, Caucasian, Hawaiian, Korean, Filipino, and Negro. The modal number of 46 was found to characterize the chromosomal complements of these seven ethnic groups, of which, the Korean, Hawaiian, and Filipino groups represented original chromosomal analyses. In addition, normal karyograms from the first four ethnic groups indicated that no significant morphological difference existed among them.-Chromosomal patterns of 13 mongoloid idiots were examined by the same technique. The modal number for each of these patients was 47, presumably of the trisomic-21 type. Analyses of the chromosomal pattern in several Caucasian, Japanese, and Hawaiian patients clearly indicated a chromosome number of 47 with trisomy for chromosome 21. BACON, D. F., Institute of Microbiology, Rutgers, The State University, New Brunswick, N. J.: Sexual transfer of the Hfr property from the K-12 strain to the W strain of Escherichia coli.-Matings of F+ cultures of strain K-12 with auxotrophs of strain W yield recombinants with very low frequency. Several Hfr cultures of K-12, however, produce recombinants with W at high frequency; in three such cases the Hfr property was transferred to the W recipient, and could be recovered after repeated backcrossings into W. The system studied in greatest detail involved culture 808 (K-12, Hfr), kindly supplied by DR. F. JACOB; this culture was crossed with a proline auxotroph (pro-) of W and pro+ recombinants were screened for their ability to transfer leucine independence (leu+) with high frequency. The kinetics of gene transfer were studied with the aid of a blendor and with phage T6. In the cross, K-12, Hfr 808 x K-12, leu-, the leucine marker entered at 6.5 minutes and the maximum number of recombinants was equivalent to 10% of the Hfr cells; in the crosses, K-12, Hfr 808 x W, leu-and W, Hfr 808 X W, leu-, the leucine marker also entered at 6.5 minutes, but the maximum recovery of recombinants was 1-2% of the Hfr cells; in the cross W, Hfr 808 x K-12, leu-, recombinants occurred with low frequency (less than 0.001% of Hfr cells). (Aided by the U. S. Public Health Service and the Office of Naval Research.) : Histoincompatibility associated with the X chromosome in mice.-During an experiment on induced mutations at the histocompatibility loci, evidence was fortuitously obtained for the existence of an unanticipated source of histoincompatibility.--Grafts were exchanged between hybrid types in like-sexed groups by means of a tail-skin grafting technique (BAILEY and USAMA, Transplantation Bull. 7: 424, 1960). Out of 36 grafts transplanted in males from (BALB/c 9 x C57BL/6 8 )F1 to (C57BL/6 9 x BALB/c 8 )F1 hybrids, 31 survived to five weeks after grafting; 14 to nine weeks. Out of 34 grafts made in the opposite direction in males, 16 survived to five weeks after grafting; none, to nine weeks. I n contrast, all 80 grafts exchanged between reciprocal hybrids in females survived to nine weeks and beyond.-Second-set grafts on five F, males were rejected in an average of ten days, suggesting that the phenomenon under observation was immunological in nature. In order to determine the relative roles played by the X and Y chromosomes, nine other sensitized F, males were challenged with grafts from both parental strains. I n all cases it was the skin of the paternal strain that was rejected. Moreover, mean survival time of these paternal-strain grafts was similar to that of second-set grafts. It is therefore concluded that the X chromosome is the bearer of one or more histocompatibility determining factors. (Supported by U. S. Atomic Energy Commission, contract AT(l1-1)-34, Proj. No. 41.) BAKER, L. H., and N. J. BECK, Hy-Line Poultry Farms, Johnston, Iowa: Genetic sampling uariation in tester female populations of poultry.-While a recurrent to tester selection program 2 X lo6 progeny scored. I n no case was there evidence for suppressor mutations. BARRATT, RAYMOND W., Dartmouth College, Hanover, N. H.: Altered proteins produced b y mutation at the amination (am) locus in Neurospora.-Mutants at the am locus in Neurospora crassa lack a T P N specific glutamic acid dehydrogenase (GAD) capable of catalyzing the amination of alpha ketoglutarate to glutamic acid. Antisera prepared against purified wild-type GAD strain 74A shows the presence of neutralizing cross-reacting proteins (CRM) in am" am, and amg . armh, am5, am6, am7, amB, amg, and amll produce no cross-reacting material. am" am" amg also complement in heterocaryons as shown by FINCHAM. GAD and CRM from wildtype 74A, am" and partial reversions ampa and amJa were isolated and purified. Each of the four proteins migrated as a single band electrophoretically, and all four had the same mobility. Tryptic digests and tryptic plus chymotryptic digests of the four proteins were compared by the fingerprint technique. Partial reversion amga was found to have a peptide absent when compared with digests of the other three strains. No additional or displaced peptide was detected on
pmid:17248125 pmcid:PMC1210393 fatcat:7pmfnacjcvealf5sodc4ebfdba