bluuebunny/crossref_metadata_2025_split huggingface dataset:
The isolation of polygenic factors controlling bristle score in Drosophila melanogaster. I. Allocation of third chromosome sternopleural bristle effects to chromosome sections.
Authors: Shrimpton A E , Robertson A 
Published: January 2021

Abstract
A single third chromosome C, with a high sternopleural bristle score, had been extracted from an artificial selection line. C was divided into five chromosomal sections by recombination with a multiply marked third chromosome ruseca, which had a low sternopleural bristle score. A nonuniform distribution of sternopleural bristle effect with physical length of chromosome was observed. The second section (26-44 cM) of C carried the most sternopleural bristle effect (10 bristles when homozygous), the first (0-26 cM) and third (44-62 cM) also carried significant sternopleural bristle effects (six and five bristles, respectively). The fourth section (62-71 cM) carried a small but significant effect (less than one bristle) while the fifth section (71-101 cM) carried little effect when alone (less than one bristle), though it did carry effects which had an epistatic interaction with those of the first and second sections.
Why do unrelated insertion sequences occur together in the genome of Escherichia coli?
Authors: Hartl D L , Sawyer S A 
Published: January 2021

Abstract
Natural isolates of Escherichia coli are polymorphic for the presence or absence of insertion sequences. Among the ECOR reference collection of 71 natural isolates studied for the number of copies of the insertion sequences IS1, IS2, IS3, IS4, IS5 and IS30, the number of strains containing no copies of the insertion sequences were 11, 28, 23, 43, 46 and 36, respectively. Significant correlations occur in the ECOR strains in the presence or absence of unrelated insertion sequences in the chromosome and plasmid complements. Strains containing any insertion sequence are more likely to contain additional, unrelated insertion sequences than would be expected by chance. We suggest that the positive correlations result from horizontal transfer mediated by plasmids. A branching-process model for the plasmid-mediated transmission of insertion sequences among hosts yields such a correlation, even in the absence of interactions affecting transposition or fitness. The predictions of the model are quantitatively in agreement with the observed correlations among insertion sequences.
Pronuclear fusion failure: an alternate conjugational pathway in Tetrahymena thermophila, induced by vinblastine.
Authors: Hamilton E P , Suhr-Jessen P B , Orias E 
Published: January 2021

Abstract
Vinblastine is shown to induce pronuclear fusion failure in conjugating Tetrahymena thermophila. In this alternate conjugational pathway gametic pronuclei are exchanged between conjugants but do not fuse. Each pronucleus undergoes one mitotic division to produce a new macro- and micronucleus. Genetic consequences of pronuclear fusion failure include the following: (1) the progeny are whole genome homozygotes with nuclei derived from single meiotic products, and (2) half of the progeny are heterokaryons with micro- and macronuclei of different genetic origins. These facts make this process extremely useful in strain construction and mutant isolation. The induction of pronuclear fusion failure by vinblastine suggests that microtubules play an essential role in pronuclear fusion.
Bipartite structure of the 5S ribosomal gene family in a Drosophila melanogaster strain, and its evolutionary implications.
Authors: Samson M L , Wegnez M 
Published: January 2021

Abstract
Knowledge of multigenic family organization should provide insight into their mode of evolution. Accordingly, we characterized the 5S ribosomal gene family in the Drosophila melanogaster strain ry506. The 5S genes in this strain display a striking HindIII restriction difference compared to the "standard" D. melanogaster 5S genes. The sequence of three ry506 5S genes was determined. We show that the HindIII restriction site heterogeneity within the ry506 5S family most probably results from the same point mutation, suggesting that a single 5S variant was propagated into the 5S cluster of this strain. Furthermore, we demonstrate that the structural organization of the 5S genes in ry506 is a bipartite structure, i.e., that about 40% of the 5S genes constitute a HindIII+/HindIII- mixed cluster, while those remaining constitute an homogeneous HindIII- cluster. The events which might lead to such an heterogeneous pattern are discussed from an evolutionary point of view.
Conditions under Which the Mean Fertility Is Maximized When a Population Is at a Stable Equilibrium.
Authors: Scott M E , Scott D M , Pollak E 
Published: January 2021

Abstract
It is assumed that there is a population with two alleles at one locus, random mating of adults and selection only involving differential fertilities. By making use of the Kuhn-Tucker theory of optimization under constraints, conditions are derived under which stable equilibrium frequencies x, y and z of the three genotypes are the same as those that maximize the mean fertility of the population. We derive all sets of frequencies of this type for the Hadeler-Liberman symmetric fertility model and all such sets for which at least one genotype is missing for the general model. If the population has frequencies that are initially near those at which there is both a stable equilibrium and maximization of the mean fertility, then the mean fertility phi(t) at time t is nondecreasing with t as t -&gt; &. It is found that it is possible for the stable equilibrium maximum points (x, y, z) to be one or two points on a ridge on which the mean fertility phi is maximized or the entire set of points on the ridge. Furthermore, phi may be smaller on this ridge than at another stable equilibrium point at which phi is not even locally maximized.
P element insertions and rearrangements at the singed locus of Drosophila melanogaster.
Authors: Roiha H , Rubin G M , O'Hare K 
Published: January 2021

Abstract
DNA from the singed gene of Drosophila melanogaster was isolated using an inversion between a previously cloned P element at cytological location 17C and the hypermutable allele singed-weak. Five out of nine singed mutants examined have alterations in their DNA maps in this region. The singed locus is a hotspot for mutation during P-M hybrid dysgenesis, and we have analyzed 22 mutations induced by P-M hybrid dysgenesis. All 22 have a P element inserted within a 700-bp region. The precise positions of 10 P element insertions were determined and they define 4 sites within a 100-bp interval. During P-M hybrid dysgenesis, the singed-weak allele is destabilized, producing two classes of phenotypically altered derivatives at high frequency. In singed-weak, two defective P elements are present in a "head-to-head" or inverse tandem arrangement. Excision of one element results in a more extreme singed bristle phenotype while excision of the other leads to a wild-type bristle phenotype.
Unlinked noncomplementation: isolation of new conditional-lethal mutations in each of the tubulin genes of Saccharomyces cerevisiae.
Authors: Stearns T , Botstein D 
Published: January 2021

Abstract
Mutations in genes of Saccharomyces cerevisiae that code for proteins that interact with beta-tubulin were sought by screening for unlinked mutations that fail to complement mutations in the single beta-tubulin-encoding gene (TUB2). Among the first three noncomplementing mutations examined, two are linked to TUB2 while one is unlinked. The unlinked mutation was shown to be a conditional-lethal allele of the major alpha-tubulin-encoding gene (TUB1) and represents the first such mutation in that gene. The tub1-1 mutation itself causes a cold-sensitive cell-cycle arrest, and confers supersensitivity to the antimicrotubule drug benomyl. These phenotypes occur in the presence of a wild-type copy of the minor alpha-tubulin-encoding gene, TUB3; the combination of tub1-1 and a tub3 null mutation is inviable in haploids. Through further application of this method, new mutations in TUB2 and TUB3 were isolated as unlinked noncomplementers of tub1-1. The noncomplementation between tub1 and tub2 mutations is gene specific and allele specific, suggesting that the phenotype is due to an interaction at the protein level. We conclude that isolation of unlinked noncomplementing mutations is likely to be a generally useful method for isolating mutations in interacting gene products.
Spontaneous mitotic recombination in yeast: the hyper-recombinational rem1 mutations are alleles of the RAD3 gene.
Authors: Montelone B A , Hoekstra M F , Malone R E 
Published: January 2021

Abstract
The RAD3 gene of Saccharomyces cerevisiae is required for UV excision-repair and is essential for cell viability. We have identified the rem1 mutations (enhanced spontaneous mitotic recombination and mutation) of Saccharomyces cerevisiae as alleles of RAD3 by genetic mapping, complementation with the cloned wild-type gene, and DNA hybridization. The high levels of spontaneous mitotic gene conversion, crossing over, and mutation conferred upon cells by the rem1 mutations are distinct from the effects of all other alleles of RAD3. We present preliminary data on the localization of the rem1 mutations within the RAD3 gene. The interaction of the rem1 mutant alleles with a number of radiation-sensitive mutations is also different than the interactions reported for previously described (UV-sensitive) alleles of RAD3. Double mutants of rem1 and a defect in the recombination-repair pathway are inviable, while double mutants containing UV-sensitive alleles of RAD3 are viable. The data presented here demonstrate that: (1) rem1 strains containing additional mutations in other excision-repair genes do not exhibit elevated gene conversion; (2) triple mutants containing rem1 and mutations in both excision-repair and recombination-repair are viable; (3) such triple mutants containing rad52 have reduced levels of gene conversion but wild-type frequencies of crossing over. We have interpreted these observations in a model to explain the effects of rem1. Consistent with the predictions of the model, we find that the size of DNA from rem1 strains, as measured by neutral sucrose gradients, is smaller than wild type.
Quantitative Genetics of Drosophila Melanogaster. II. Heritabilities and Genetic Correlations between Sexes for Head and Thorax Traits.
Authors: Cowley D E , Atchley W R 
Published: January 2021

Abstract
A quantitative genetic analysis is reported for traits on the head and thorax of adult fruit flies, Drosophila melanogaster. Females are larger than males, and the magnitude of sexual dimorphism is similar for traits derived from the same imaginal disc, but the level of sexual dimorphism varies widely across discs. The greatest difference between males and females occurs for the dimensions of the sclerotized mouthparts of the proboscis. Most of the traits studied are highly heritable with heritabilities ranging from 0.26 to 0.84 for males and 0.27 to 0.81 for females. In general, heritabilities are slightly higher for males, possibly reflecting the effect of dosage compensation on X-linked variance. The X chromosome contributes substantially to variance for many of these traits, and including results reported elsewhere, the variance for over two-thirds of the traits studied includes X-linked variance. The genetic correlations between sexes for the same trait are generally high and close to unity. Coupled with the small differences in the traits between sexes for heritabilities and phenotypic variances, these results suggest that selection would be very slow to change the level of sexual dimorphism in size of various body parts.
Unidirectional incompatibility in Drosophila simulans: inheritance, geographic variation and fitness effects.
Authors: Hoffmann A A , Turelli M 
Published: January 2021

Abstract
In California, Drosophila simulans females from some populations (type W) produce relatively few adult progeny when crossed to males from some other populations (type R), but the productivity of the reciprocal cross is comparable to within-population controls. These two incompatibility types are widespread in North America and are also present elsewhere. Both types sometimes occur in the same population. Type R females always produce type R progeny irrespective of the father's type. However, matings between R males and females from stocks classified as type W produce type R progeny at low frequency. This suggests rare paternal transmission of the R incompatibility type, as we have found no evidence for segregation of incompatibility types in the W stocks. There is quantitative variation among type R lines for compatibility with W females, but not vice versa. Population cage studies and productivity tests suggest that deleterious side effects are associated with the type R cytoplasm.
Microgeographic genetic variation in the apple maggot rhagoletis pomonella.
Authors: McPheron B A , Smith D C , Berlocher S H 
Published: January 2021

Abstract
We examined electrophoretic variability at five enzyme loci in the apple maggot fly, Rhagoletis pomonella, on a microgeographic scale. Treating flies from individual hawthorn trees as separate populations, we estimated F(ST) values from allele frequencies. The results indicate that there is significant allele frequency heterogeneity among fly populations over a small spatial scale at some loci but not at others. This variation among loci in degree of differentiation is itself statistically significant, casting doubt on the role of genetic drift in maintaining the heterogeneity. There is also heterogeneity between years in flies from a given tree. These data provide a baseline with which future work on genetic differentiation among apple maggot populations associated with different species of host plants may be compared.
Effects of an intercultivaral chromosome substitution on winterhardiness and vernalization in wheat.
Authors: Zemetra R S , Morris R 
Published: January 2021

Abstract
During a study on the genetic control of winterhardiness in winter wheat (Triticum aestivum L. group aestivum), a gene that affected vernalization was found on chromosome 3B in the winter wheat cultivar ;Wichita.' When chromosome 3B from Wichita was substituted into the winter wheat cultivar ;Cheyenne,' the resultant substitution line exhibited a spring growth habit. This is unusual since a cross between the cultivars Wichita and Cheyenne results in progeny that exhibit the winter growth habit. The F(2) plants from a cross of the 3B substitution line to Cheyenne, the recipient parent, segregated 3:1 for heading/no heading response in the absence of vernalization (chi(2) = 2.44). Earliness of heading appeared to be due to an additive effect of the 3B gene as shown by the segregation ratio 1:2:1 (early heading-later heading-no heading) (chi(2) = 2.74). This vernalization gene differs from previously described vernalization genes because, while dominant in a Cheyenne background, its expression is suppressed in Wichita. The gene may have an effect on winter hardiness in Wichita. In a field test for winter survival the 3B substitution line had only 5% survival, while Wichita and Cheyenne had 50 and 80% survival, respectively. No other substitution line significantly reduced winter survival. The difference between Wichita and Cheyenne in winterhardiness may be due to the vernalization gene carried on the 3B chromosome.
Isolation and characterization of mutants which show an oversecretion phenotype in Saccharomyces cerevisiae.
Authors: Sakai A , Shimizu Y , Hishinuma F 
Published: January 2021

Abstract
We have isolated mutants responsible for an oversecretion phenotype in Saccharomyces cerevisiae, using a promoter of SUC2 and the gene coding for alpha-amylase from mouse as a marker of secretion. These mutations defined two complementation groups, designated as ose1 (over secretion) and rgr1 (resistant to glucose repression). The ose1 mutant produced an oversecretion of amylase by 12- to 15-fold under derepressing conditions; however, the amylase mRNA was present at nearly the same amount as it was in the parent cells. No expression of the amylase gene was detected under repressing conditions. The rgr1 mutant oversecreted amylase by 11- to 13-fold under repressing conditions by 15- to 18-fold under derepressing conditions. The rgr1 mutant showed pleiotropic effects on the following cellular functions: (1) resistance to glucose repression, (2) temperature-sensitive lethality, (3) sporulation deficieny in homozygous diploid cells, and (4) abnormal cell morphology. The rgr1 mutation was not allelic with ssn6 and cyc9, and failed to suppress snf1.
Genetic analysis of chromosomal region 67A-D of Drosophila melanogaster.
Authors: Leicht B G , Bonner J J 
Published: January 2021

Abstract
In an effort to (1) characterize the 67 interval of chromosome 3 of Drosophila melanogaster genetically and (2) isolate mutations of the 67B1 small heat shock protein (hsp) gene cluster specifically, we undertook a mutational analysis of the 67A-D subinterval. Using a deficiency of the 67A2 to 67D11-13 region, Df(3L)AC1, we screened 8700 diepoxybutane-treated chromosomes and 7800 ethyl methanesulfonate-treated chromosomes for visible and lethal mutations throughout this interval and recovered 74 independent recessive lethal mutations, but no visible mutations. One of the lethal mutations, d29A6, was identified as an overlapping deficiency extending from 66F3 to 67B1. An additional 6000 diepoxybutane-treated chromosomes were screened for lethality over d29A6, yielding another four lethal mutations within the 67A2-B1 subinterval. These 78 lethal mutations, along with two others isolated in other laboratories, define 23 essential loci--6 within the 67A2-B1 subinterval and 17 within the 67A2 to D11-13 subinterval. Many of these loci appear to be required for imaginal development only, exhibiting late larval to pharate adult lethal phases. Examination of the 67A2-B1 lethal complementation groups for (1) earlier onset of lethality following a heat shock, (2) missing or altered small hsps on two-dimensional protein gels, and (3) restoration of viability by transformed wild-type copies of the small hsp genes indicates that none of these mutations affect the small hsps. On the basis of this analysis and the known homology of the genes, we conclude that the small hsps are functionally equivalent.
A genetic analysis of male-predominant pheromones in Drosophila melanogaster.
Authors: Scott D , Richmond R C 
Published: January 2021

Abstract
Chemical signals from males play an important role in stimulating Drosophila melanogaster females to mate, and male-predominant pheromones may influence a female's choice of mates. Male-predominant pheromones also inhibit courtship, thereby functioning as antiaphrodisiacs. Interstrain variation in the ratio of two male-predominant pheromones (7-tricosene and 7-pentacosene) has been reported, but the genetic basis for this potentially important variation has not been examined. In a series of crosses between strains that differ radically in the amounts of 7-tricosene and 7-pentacosene, we have identified both X-linked and autosomal contributions to interstrain variation in the amounts of these compounds. The X-linked loci act as enhancers for production of the compound predominant in the strain from which the X chromosome originated. Autosomal factors for each of the two compounds appear to segregate as high vs. low, with incomplete dominance of high 7-tricosene over low, and low 7-pentacosene over high. A significant negative correlation between the quantities of 7-pentacosene and 7-tricosene in the F2 and backcross progeny, but not in the F1s or parentals, indicates linkage between autosomal loci regulating the expression of each compound. However, the phenotypic distributions of the backcross progeny indicate that additional unlinked loci are also directly involved in the production of these two hydrocarbons.
Estimation of mutation rates based on the analysis of polypeptide constituents of cultured human lymphoblastoid cells.
Authors: Chu E H , Boehnke M , Hanash S M , Kuick R D , Lamb B J , Neel J V , Niezgoda W , Pivirotto S , Sundling G 
Published: January 2021

Abstract
A subclone of a human diploid lymphoblastoid cell line, TK-6, with consistently high cloning efficiency has been used to estimate the rates of somatic mutations on the basis of protein variation detected by two-dimensional polyacrylamide gel electrophoresis. A panel of 267 polypeptide spots per gel was screened, representing the products of approximately 263 unselected loci. The rate of human somatic mutation in vitro was estimated by measuring the proportion of protein variants among cell clones isolated at various times during continuous exponential growth of a TK-6 cell population. Three mutants of spontaneous origin were observed, giving an estimated spontaneous rate of 6 x 10(-8) electrophoretic mutations per allele per cell generation (i.e., 1.2 x 10(-7) per locus per cell generation). Following treatment of cells with N-ethyl-N-nitrosourea, a total of 74 confirmed variants at 54 loci were identified among 1143 clones analyzed (approximately 601,000 allele tests). The induced variants include 65 electromorphs which exhibit altered isoelectric charge and/or apparent molecular weight and nine nullimorphs for each of which a gene product was not detected at its usual location on the gel. The induced frequency for these 65 structural gene mutants is 1.1 x 10(-4) per allele. An excess of structural gene mutations at ten known polymorphic loci and repeat mutations at these and other loci suggest nonrandomness of mutation in human somatic cells. Nullimorphs occurring at three heterozygous loci in TK-6 cells may be caused by genetic processes other than structural gene mutation.
Genetic control of intrachromosomal recombination in Saccharomyces cerevisiae. I. Isolation and genetic characterization of hyper-recombination mutations.
Authors: Aguilera A , Klein H L 
Published: January 2021

Abstract
Eight complementation groups have been defined for recessive mutations conferring an increased mitotic intrachromosomal recombination phenotype (hpr genes) in Saccharomyces cerevisiae. Some of the mutations preferentially increase intrachromosomal gene conversion (hpr4, hpr5 and hpr8) between repeated sequences, some increase loss of a marker between duplicated genes (hpr1 and hpr6), and some increase both types of events (hpr2, hpr3 and hpr7). New alleles of the CDC2 and CDC17 genes were recovered among these mutants. The mutants were also characterized for sensitivity to DNA damaging agents and for mutator activity. Among the more interesting mutants are hpr5, which shows a biased gene conversion in a leu2-112::URA3::leu2-k duplication; and hpr1, which has a much weaker effect on interchromosomal mitotic recombination than on intrachromosomal mitotic recombination. These analyses suggest that gene conversion and reciprocal exchange can be separated mutationally. Further studies are required to show whether different recombination pathways or different outcomes of the same recombination pathway are controlled by the genes identified in this study.