bluuebunny/crossref_metadata_2025_split huggingface dataset:
DYNAMICS OF CORRELATED GENETIC SYSTEMS. V. RATES OF DECAY OF LINKAGE DISEQUILIBRIA IN EXPERIMENTAL POPULATIONS OF DROSOPHILA MELANOGASTER
Authors: Clegg M T , Kidwell J F , Horch C R 
Published: April 2021

ABSTRACT
The dynamic behavior of four-locus gametic frequency distributions was studied in five replicate cage populations of Drosophila melanogaster for up to 50 generations. The joint frequency distributions were resolved into gene freqcencies and various disequilibrium measures. In addition, F statistics for marginal single-locus genotypic frequency distributions were followed through time. The gene frequency, disequilibrium and F statistics were obtained for four chromosome 3 enzyme marker loci [isocitrate dehydrogenase (3-27.1), esterase4 (3-36.8). phosphoglucomutase (343.4) and esterase-c (3-49.0)]. The initial structure of the experimental populations featured random mating proportions, and two complementary gametic types with respect to the marker loci, thus assuring complete pairwise linkage disequilibrium among the markers.—The experimental results indicate: (1) the between-replicate variance in gene frequency varied substantially among loci, with isocitrate dehydrogenase showing the greatest between-replicate variance, and esterase-C the least. (2) The F statistics initially were strongly negative but decayed to the neighborhood ofzero for all marker lociexcept esterase-C. The rate at which the F statistics approached zero varied among the marker loci, indicating substantial differences in the distribution of selective effects along the chromosome. The centromeric region, marked by esterase-C, shows the strongest selective effects. (3)The rate of decay 3flinkage disequilibrium was much faster than expected for pairs of neutral loci, averaging 1.82times the neutral rate over all replicates and pairs of loci. This acceleration, which was observed for all six pairwise combinations of loci, was interpreted asresulting from the interaction bctween selection and recombination. Our experimental results are consistent with many investigations of linkage disequilibrium in natural populations of Drosophila melanogasler that show little or no disequilibrium among enzyme loci. (4) Afortuitous contamination of two cages revealed an apparent regulatory interaction between the migrant and nonmigrant chromosomes at the esterase-C locus. The migrant chromosomes were very rapidly absorbed into the recipient populations, despite this interaction. This result suggests that the dynamics of migration in populations may be phenomenologically richer than anticipated by simple theory.
DEFINITION OF ADDITIONAL FLAGELLAR GENES IN ESCHERICHIA COLI K12
Authors: Komeda Yoshibumi , Kutsukake Kazuhiro , Iino Tetsuo 
Published: April 2021

ABSTRACT
Twentynine flagellar genes in Escherichia coli K12 have previously been assigned to three regions of the genome. Flagellar region I is located between pyrC and ptsG, region I1 between aroD and uvrC, and region I11 between uvrC and his. In this study, flagellar mutants in EscherLchia coli K12 were obtained by selection for resistance to the flagellotropic phage, x. They were analyzed in complementation tests using PI phage-mediated transduction. In addition to the fla genes already described, eight more flagellar genes were identified. This analysis defined six more fla genes in region I (flaU, etc.), one more in region I1 (fZbB) and one more in region I11 (flbC) . Region I was shown to include at least 12 fla cistrons. Complementation analysis with polar Muphage-induced Fla- mutants and with λfla phage defined four transcriptional units in region I. These were: flaU, flbA-flaw-flav-flaK-flax-flaL-flay-flaM, fluz and flaS-flaT, with transcription proceeding from left to right. The flbB gene was found to be part of an operon: flbB-flal in region 11. In region 111, a previously unidentified gene flbC was located between hag and flaN.
THE MEIOTIC EFFECTS OF A DEFICIENCY IN DROSOPHILA MELANOGASTER: IDENTIFICATION OF TWO DOSAGE-SENSITIVE SITES
Authors: Robbins Leonard G 
Published: April 2021

ABSTRACT
Heterozygosity for a deficiency for the entire zeste-white region of the X chromosome of Drosophila melanogaster females causes both reduced recombination and increased nondisjunction. The location of the dosage-sensitive sites responsible for these two meiotic defects has been studied by use of a set of deficiencies that subdivide the region. Recombination is reduced when the zw7-zwll region is present in one dose, while nondisjunction is increased only if the doses of both the zw8-zwl0 and zwb-zwll segments are reduced. Examination of truns heterozygotes of two deficiencies explicitly demonstrates the compound nature of the meiotic dose effect and further delimits the location of the proximal disjunctional site to the zwl2-zwll interval. In inversion/deficiency heterozygotes, reduced dose ofthe zw8-zwl0 region alone, without reduced dose of the proximal site, yields increased nondisjunction, suggesting that the proximal element that affects disjunction is the same as that which affects recombination. Thus, the zeste-white region contains at least two dosagesensitive loci that affect meiosis: reduced dosage of one locus, in the zw7-zwfl interval, causes reduced recombination; reduced dose of another, in the zw8-zw10 region, increases the probability that nonexchange chromosomes will nondisjoin. Aslight effect on the regional distribution of exchange may also be a property of the zw8-zwlO region locus, but could be an effect of yet another locus or of structural heterozygosity. The implications of these results for understanding meiotic control and the prospects for further analysis of the structure of the zeste-white interval are considered.
PLEIOTROPIC EFFECTS ON FITNESS OF MUTATIONS AFFECTING VIABILITY IN DROSOPHILA MELANOGASTER
Authors: Simmons Michael J , Preston Christine R , Engels William R 
Published: April 2021

ABSTRACT
The relative viabilities and fitnesses of wild-type second chromosomes in heterozygous condition were determined. Joint analysis of these permitted an estimation of a parameter that relates the viability effect of a mutation to its effect on fitness as a whole. For newly arisen mutations, the estimate was slightly greater than one, indicating that the reductions in viability caused by these mutations are associated with reductions in other components of fitness. For mutations from an equilibrium population, the estimate of the parameter was near zero, implying that the deleterious viability effects of these mutations arc compensated by improvements in other aspects of fitness.
NUMERICAL ANALYSIS OF RANDOM DRIFT IN A CLINE
Authors: Nagylaki Thomas , Lucier Bradley 
Published: April 2021

ABSTRACT
The equilibrium state of a diffusion model for random genetic drift in a cline is analyzed numerically. The monoecious organism occupies an unbounded linear habitat with constant, uniform population density. Migration is homogeneouq symmetric and independent of genotype. A single diallelic locus with a step environment is investigated in the absence of dominance and mutation. The flattening of the expected cline due to random drift is very slight in natural populations. The ratio of the variance of either gene frequency to the product of the expected gene frequencies decreases monotonically to a nonzero constant. The correlation between the gene frequencies at two points decreases monotonically to zero as the separation is increased with the average position fixed; the decrease is asymptotically exponential. The correlation decreases monotonically to a positive constant depending on the separation as the average position increasingly deviates from the center of the cline with the separation fixed. The correlation also decreases monotonically to zero if one of the points is fixed and the other is moved outward in the habitat, the ultimate decrease again being exponential. Some asymptotic formulae are derived analytically.—The loss of an allele favored in an environmental pocket is investigated by simulating a chain of demes exchanging migrants, the other assumptions being the same as above. For most natural populations, provided the allele would be maintained in the population deterministically, this process is too slow to have evolutionary importance.
HITCHHIKING: A COMPARISON OF LINKAGE AND PARTIAL SELFING
Authors: Hedrick Philip W 
Published: April 2021

ABSTRACT
Genetic hitchhiking occurs when alleles at unselected loci are changed in frequency because of an association with alleles at a selected locus. This association may be mediated either by linkage or partial selfing (inbreeding) and can affect the gene frequency and gametic disequilibrium at the neutral loci. Hitchhiking from partial selfing (unlinked loci) occurs more quickly than linkage hitchhiking and generally has a greater effect. In addition, partial-selfing hitchhiking can cause increases or changes in sign in gametic disequilibrium between neutral loci. The effects of the two types of hitchhiking with different levels of dominance, zygotic frequencies and number of selected loci are also examined. The general conditions for linkage and partial-selfing hitchhiking are outlined and the implications of hitchhiking are discussed for marker or electrophoretic loci.
PLEIOTROPIC PROPERTIES OF A YEAST MUTANT INSENSITIVE TO CATABOLITE REPRESSION
Authors: Stark Helene Cherrick , Fugit Donna , Mowshowitz Deborah Bernhardt 
Published: April 2021

ABSTRACT
The flk1 mutation, which was originally isolated in the yeast Saccharomyces cadsbergenesis, causes insensitivity to catabolite repression. This mutation has been further characterized and mapped. The gene flkl is located on chromosome III between thr4 and MAL2,14 centimorgans from MAL2. flk1 is shown to be allelic to the pleiotropic mutants tupl, cyc9, and umr7; and flk1 is shown to exhibit an array of pleiotropic properties common to tupl, cyc9 and umr7; These results suggest that the flkl mutation is not a specific lesion affecting catabolite repression.
GENETIC MAPPING OF THE pho2, PHO82–pho4 AND pho85 LOCI OF YEAST
Authors: Toh-E Akio 
Published: April 2021

ABSTRACT
The PH082-pho4 (PHOO-phoD) locus was mapped on the right arm of chromosome VI,6.5 cM centromere-distal to met10. A pho85 (phoU) mutant was newly isolated, and its map location was determined on the left arm of chromosome XVI, 15 cM centromere-distal to rad1. Amutant gene that causes temperature-sensitive growth on nutrient medium was found very near (or at) the pho85 locus. The supertriploid method was successfully applied to locate the pho2 (phoB) locus on chromosome IV. The pho2 locus was 40 cM from rna11 on the left arm of chromosome IV.
COMPONENTS OF HYBRID DYSGENESIS IN A WILD POPULATION OF DROSOPHILA MELANOGASTER
Authors: Engels William R , Preston Christine R 
Published: April 2021

ABSTRACT
Hybrid dysgenesis is a condition foand in certain interstrain hybrids of Drosophila melanogrrster caused by the interaction of chromosomal and cytoplasmic factors. Germ line abnormalities, including sterility, high mutability and male recombination, appear in the affected individuals. There are at least two distinct systems of hybrid dysgenesis. We examined a Wisconsin wild populetion in two consecutive years to determine the distribution of the chromosomal P factor and the extrachromosomal M cytotype that together cause one kind of hybrid dysgonic sterility. The P factor was found to be very common in the populetion, with all three major chromosomes heing polymorphic for it. This polymorphism was strongly correlated with variability for male recombination elements, suggesting that these two traits are part of the same system of hybrid dysgenesis. There was a slight tendency for the P factor to be lost in lines taken from this population and inbred in the laboratory for many generations. A large-scale search for the M cytotype, which causes susceptibility to the P factor, showed that it is present in the papulation at only very low frequencies. Further evidence that the population is mostly immune to the action of the P factor was our finding of a general lack of dysgenic sterility in the wild flies themselves. However, we were able to isolate several wild strains that consistently showed the M cytotype. In some cases, the frequency of the M cytotype could be maintained in these lines, but it could not usually be increased by artificial sclection. Some possible consequences of hybrid dysgenesis for the evolutional y Siology of Drosophila are suggested.
MAPPING OF THE polA LOCUS OF ESCHERICHIA COLI K12: GENETIC FINE STRUCTURE OF THE CISTRON
Authors: Kelley William S 
Published: April 2021

ABSTRACT
The close linkage of the glnA gene with polA was exploited to construct a fine structure map of polA by means of generalized transduction with phage P1. Nine different polA- alleles were mapped by recombinational crosses. The results indicate a gene order consistent with previous observations (KELLEYand GRINDLEY 19 76a; MURRAY an d KELLEY 1979). Three mutations, polA5, polA6 and polA12 map within the "carboxy-terminal" or "large-fragment'' portion of the gene in unambiguous order. Four alleles, known to affect the "aminoterminal" portion of the gene, polA107, polA214, polA480ex and polA4113, appear to be closely linked with certain ambiguities in their exact order. All four of these mutations are known to alter the 5'→3' exonuclease activity of DNA polymerase I and three of them result in the conditional lethal polA- phenotype. The polA1 nonsense mutation maps between these two groups in a position consistent with its known effect, production of an amber fragment that includes the 5'→3' exonuclease. The final allele, resAl, is another nonsense mutation that maps at; the extreme "amino-terminus" of the cistron.—A number of control experiments were conducted to determine the effects of pol.A- mutatims on the PI-mediated recombinational event. These experiments indicated that abortive transduction occurs quite frequently, but the formation of abortive transductants and segregation of unselected transduced markers among daughter progeny is like that observed by other investigators. There was no evidence that any individual polA- allele behaved in an exceptional fashion during recombination.
MATHEMATICS OF CHROMOSOME PAIRING
Authors: Driscoll C J , Gordon G H , Kimber G 
Published: April 2021

ABSTRACT
Analysis of frequencies of chromosome configurations in wheat-related species hybrids is extended to include cases involving homoeologous groups of size six. Further, the expected frequencies of the various configurations emanating from homologous and homoeologous pairing events have been determined for groups consisting of two and three homoeologous pairs of homologous chromosomes. Analysis of configuration frequencies of nullisomic 5B of wheat, in which both homologous and homoeologous pairing occurs, led to estimation of the relative frequencies of homologous and homoeologous pairing events as 17.9: 1. In the samples analyzed, slightly less than one homoeologous exchange occurred per gamete.
A METHOD FOR COMPLEMENTATION ANALYSIS OF NUCLEAR AND CHLOROPLAST MUTANTS OF PHOTOSYNTHESIS IN CHLAMYDOMONAS
Authors: Bennoun Pierre , Masson Arlette , Delosme Monique 
Published: April 2021

ABSTRACT
The photosynthetic properties of young zygotes of Chlamydomonas reinhardi were analyzed. In heterozygotes for two nuclear or two chloroplast mutations affecting photosynthesis, recovery of photosynthetic activity was observed that is most likely the result of intergenic complementation.—We observed that chloramphenicol inhibited the recovery of activity in double heterozygotes for mutants lacking at least one thylakoid polypeptide of chloroplast origin, while it had no effect on wild-type homozygotes. This indicates that the recovery of activity in double heterozygotes could result from the repair of existing thylakoid membranes by de nouo synthesis of the missing polypeptides.
HETERODUPLEX REPAIR AS AN INTERMEDIATE STEP OF UV MUTAGENESIS IN YEAST
Authors: Eckardt Friederike , Teh Soo-Jeet , Haynes R H 
Published: April 2021

ABSTRACT
We have measured UV-induced mutation frequencies in yeast in a forward, nonselective assay system by scoring white adex ade2 double auxotrophs among parental red-pigmented ade2 clones. The frequencies of sectored and pure mutant clones were determined separately. In excision-defective strains carrying the genes radl-1, rad3-2 and rad4-4, as well as in the double mutants, rad 1-1 rad 3-2 and rad 1-1 rad 4-4, considerably more sectored than pure clones are induced in the low-dose range; in repair-competent strains, pure mutant clones substantially outnumber the sectored clones. These results can be explained on the basis of known differences in the timing of error-prone repair during the cell division cycle; that is, we assume that error-prone repair occurs primarily before replication in RAD wild-type strains but after replication in excision-deficient mutants. It has been suggested that excision deficiency has a pleiotropic effect on heteroduplex repair and nucleotide excision repair; however, the high percentage (36.6%) of half-sectored clones found in the rad1-1 strain is hard to reconcile with this hypothesis. We propose that heteroduplex repair occurs subsequent to error-prone repair in both excisionproficient and excision-deficient strains.
REVERSION FROM SUPPRESSION TO NONSUPPRESSION IN SUQ5 [psi
+] STRAINS OF YEAST: THE CLASSIFICATION OF MUTATIONS
Authors: Cox B S , Tuite M F , Mundy C J 
Published: April 2021

ABSTRACT
Reversion from the suppressed to nonsuppressed phenotype in strains of genotype SUQ5 [psi +] ade2-1 his5-2 lys1-1 can1-100 ura3-1 has been induced by treatment with ethyl methanesulphonate, nitrosoguanidine or UV (254 nm) light. Spontaneously occurring revertants have also been selected by two different methods. Reversion has been shown to occur through a variety of nuclear mutations and through mutation of [psi +] to [psi -]. Nuclear mutations included back-mutation of SUQS, antisuppressor mutations that were recessive, semi-dominant or dominant, and dominant or recessive mutations of genes required for the maintenance of the [psi +] factor. Complementation tests by which the various kinds of mutations could be distin guished from one another were designed. The spectra of spontaneously occurring and induced mutations have been described.
JOINT SEGREGATION OF BIOCHEMICAL LOCI IN SALMONIDAE. II. LINKAGE ASSOCIATIONS FROM A HYBRIDIZED SALVELINUS GENOME (S. NAMAYCUSH x S. FONTINALIS)
Authors: May Bernie , Stoneking Mark , Wright James E 
Published: April 2021

ABSTRACT
The results of more than 300 parwise examinations of biochemical loci for joint segregation in brook trout (Salvelinus fontinalis) and in the hybridized genome of lake trout (S. namaycush) × brook trout are summarized. Nineteen loci have been assigned to the following eight linkage groupings on the basis of nonrandom assortment, including cases of both classical linkage and pseudolinkage: ODH with PMI with PGI-3, PGI-2 with SDH, ADA-1 with AGP-2, AAT-(1,2) with AGP-1 with MDH-I, MDH-3 with MDH-4, LDH-3 with LDH-4, IDH-3 with ME-2 and GUS with CPK-I. Pseudolinkage (an excess of nonparental progeny types) was observed only for male testcross parents. The results suggest that this phenomenon involves homeologous chromosome arms as evidenced by the de novo association of presumed duplicate loci in each case. Classical linkage has not been found for the five pairs of duplicate loci examined in Salvelinus, suggesting that not all of the eight metacentrics in the haploid complement involve fusions of homeologous chromosomes. Females consistently showed a greater degree of recombination.
FRAMESHIFT SUPPRESSION IN SACCHAROMYCES CEREVISIAE. II. GENETIC PROPERTIES OF GROUP II SUPPRESSORS
Authors: Culbertson Michael R , Underbrink Karen M , Fink Gerald R 
Published: April 2021

ABSTRACT
Suppressors of ICR-induced mutations that exhibit behavior similar to bacterial frameshift suppressors have been identified in the yeast Saccharomyces cerevisiae. The yeast suppressors have been divided into two groups. One of these groups (Group II: SUFI, SUF3, SUF4, SUF5 and SUF6) appears to include a set of informational suppressors in which the vehicle of suppression is glycyl-tRNA. Some of the genetic properties of Group II suppressors are described in this communication.—Corevertants of the Group II frameshift mutations his4-519 and leu2-3 have been characterized to determine the spectrum of reversion events induced by the frameshift mutagen ICR-170. Seventythree ICR-induced corevertants were analyzed. With the exception of one corevertant, which carried an allele of SUF1, all carried alleles of SUF3 or SUF5, SUF1, SUF3, SUF4 and SUF6 were represented among spontaneous and UV-induced corevertants. In the course of these experiments one of the suppressors was mapped. SUF5, the probable structural gene for tRNAGLY1, is located between ade2 and ade9 on chromosome XV.—SUF1, SUF4 and SUF6 have novel properties and comprise a distinct subset of suppressors. Although these suppressors show no genetic linkage to each other, they share several common features including lethality in haploid pairwise combinations, reduced tRNAGLY3 isoacceptor activity and increased efficiency of suppression in strains carrying the cytoplasmically inherited [PSI] element. In addition, strains carrying SUFI, SUF4 or SUF6 are phenotypically unstable and give rise to mitotic Suf+ segregants at high frequency. These segregants invariably contain a linked, second-site mutation that maps in or adjacent to the suppressor gene itself. Strains carrying any of these suppressors also give rise to mitotic segregants that exhibit enhanced efficiency of suppression; mutations responsible for this phenotype map at two loci, upf1 and upf2. These genes show no genetic linkage to any of the Group II suppressors.—Methods that permit positive selection for mutants with decreased or enhanced efficiency of suppression have been devised in order to examine large numbers of variants. The importance of these interacting mutants is underscored by their potential utility in studying suppressor function at the molecular level.
MUTATIONS AFFECTING SYNTHESIS OF β-GALACTOSIDASE ACTIVITY IN THE YEAST KLUYVEROMYCES LACTIS
Authors: Sheetz R Michael , Dickson Robert C 
Published: April 2021

ABSTRACT
Fifty-one mutants of Kluyveromyces lactis that cannot grow on lactose (Lac-) were isolated and characterized. All of the mutations are in nuclear genes, are recessive in their wild-type allele and define seven complementation groups, which we designate lac3 through lac9. Strains bearing mutations in lac3,lac5, lac7, lac8 and lac9 are also unable to grow on galactose (Gal-). Since the Gal- and Lac- phenotype co-segregate, they are probably due to a single mutation. Strains bearing mutations in any of the seven complementation groups grow normally on glucose. However, strains bearing mutations in lac3, lac5 and lac6 do not grow on glucose if lactose is also present in the medium. Likewise, strains bearing mutations in lac3 and lac5 do not grow on glucose in the presence of galactose. Complementation groups lac4 and lac5 are loosely linked and map within a cluster of auxotrophic mutations on a chromosome that we designate Chromosome 2. The remaining five groups are unlinked. Thus, there is no evidence for clustering of Lac genes into an operon-like regulatory unit.—To further characterize the nature of the Lac- phenotype, the basal and inducible level of β-galactosidase activity were measured. All mutants had nearly normal basal enzyme levels, except those in lac4, which had barely detectable levels. Inducible enzyme levels varied from barely detectable levels in mutants bearing lac4 mutations up to four-fold inducible levels in strains bearing mutations in other complementation groups. In all cases, however, induction levels were below the 30-fold level obtained in wild-type cells. Three strains bearing lac5 mutations contain increased enzyme activity in the absence of inducer, indicating constitutive synthesis of β-galactosidase. In summary, these data indicate that several genes are necessary for synthesis of β-galactosidase activity.