bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fitness of allozyme variants inDrosophila pseudoobscura: II. Selection at theEst-5, OdhandMdh-2loci
Authors: Marinković Dragoslav , Ayala Francisco J. 
Published: September 2009

SUMMARYWe have studied the effects on fitness of allelic variation at three gene loci (Est-5, Odh, andMdh-2)coding for enzymes inDrosophila pseudoobscura. Genotype has a significant effect on fitness for all six parameters measured (female fecundity, male mating capacity, egg-to-adult survival under near-optimal and under competitive conditions, and rate of development under near-optimal and under competitive conditions). No single genotype is best for all six fitness parameters; rather, genotypes with superior performance during a certain stage of the life-cycle may have low fitness at some other stage, or in different environmental conditions. Heterozygotes are sometimes best when all fitness parameters are considered. There are significant interactions between loci. The various forms of balancing selection uncovered in our experiments may account for the polymorphisms occurring in natural populations ofD. pseudoobscuraat the three loci studied.
The effect of population subdivision on two loci without selection
Authors: Feldman Marcus W. , Christiansen Freddy Bugge 
Published: September 2009

SUMMARYThis paper is devoted to the study of the effects of population subdivision on the evolution of two linked loci. Two simple deterministic models of population subdivision without selection are investigated. One is a finite linear ‘stepping stone’ model and the other is a finite linear stepping stone chain of populations stretching between two large populations of constant genetic constitution. At equilibrium in the first model the gene frequencies in each population are equal and there is linkage equilibrium in each population. The rate of decay to zero of the linkage disequilibrium functions is the larger of (1 –c) and, where λ1is the rate of convergence of the gene frequencies to equilibrium and c is the recombination frequency. In the second model at equilibrium there will be a linear cline in gene frequencies connecting the two large constant populations. This cline will be accompanied by a ‘cline’ of linkage disequilibria. The rate of convergence to this equilibrium cline is independent of the recombination frequency, and, in fact, the gene frequencies and the linkage disequilibria converge to equilibrium at the same rate.
Uncorrelated genetic drift of gene frequencies and linkage disequilibrium in some models of linked overdominant polymorphisms
Authors: Felsenstein Joseph 
Published: September 2009

SUMMARYFor large population sizes, gene frequenciespandqat two linked over-dominant loci and the linkage disequilibrium parameterDwill remain close to their equilibrium values. We can treat selection and recombination as approximately linear forces onp, qandD, and we can treat genetic drift as a multivariate normal perturbation with constant variance-covariance matrix. For the additive-multiplicative family of two-locus models,p, qandDare shown to be (approximately) uncorrelated. Expressions for their variances are obtained. When selection coefficients are small the variances ofpandqare those previously given by Robertson for a single locus. For small recombination fractions the variance ofDis that obtained for neutral loci by Ohta & Kimura. For larger recombination fractions the result differs from theirs, so that for unlinked loci r2≃ 2/(3N) instead of 1/(2N). For the Lewontin-Kojima and Bodmer symmetric viability models, and for a model symmetric at only one of the loci, a more exact argument is possible. In the asymptotic conditional distribution in these cases, various ofp, qandDare uncorrelated, depending on the type of symmetiy in the model.
Selection for growth-rate during asexual and sexual propagation in Phytophthora cactorum
Authors: MacIntyre Donald , Elliott Charles G. 
Published: September 2009

SUMMARYSelection for high and low growth-rate was carried out during eight generations of asexual propagation by zoospores and seven generations of sexual reproduction by oospores. The fungus has previously been shown to be diploid during its vegetative phase. In the zoospore lines there was no significant variation and no response to selection, except for the occasional appearance of fast-growing sectors. A high line was established from such a sector; in its sexual progeny the inheritance of growth-rate was non-Mendelian. Propagation through self-fertilized oospores released very considerable genetic variation, and both high and low lines responded to selection. At first the variation within families, and the response to selection, increased with succeeding generations, despite the intense inbreeding. In later generations the high line became less variable, and the progeny oospore cultures resembled the fast-growing sectors. It is concluded that growth-rate is controlled by a polygenic system and by cytoplasmic determinants, a mutant form of which is responsible for the fast-sectoring phenotype.
The lactose system inKlebsiella aerogenesV9A: 4. A comparison of thelacoperons ofKlebsiellaandEscherichia coli
Authors: Reeve E. C. R. , Braithwaite J. A. 
Published: September 2009

SUMMARYKlebsiella aerogenesV9A contains twolacoperons, one chromosomal and one borne by the Lac plasmid,FKlac. It is shown that the plasmid Lac repressor resembles that ofEsherichia coliin that it represses theE. colioperon but is inactivated by melibiose. In contrast, the chromosomal Lac repressor of V9A is unable to repress theE. colioperon or the FKlacoperon, but is converted into an active repressor of both these operons on becoming bound to melibiose. The chromosomal Lac repressor is able to repress its own operon whether or not it is bound to melibiose, but is inactivated by isopropyl-β-D-thiogalactoside. These results support the hypothesis that theKlebsiellaLac plasmid was derived from an ancestralE. colichromosome.
Six new loci controlling resistance top-fluorophenylalanine inAspergillus nidulans
Authors: Srivastava Sheela , Sinha Umakant 
Published: September 2009

SUMMARYTwelve FPA-resistant mutants were selected on medium containingp-fluorophenylalanine and ethionine. Dominance tests in heterozygous diploids showed that 8 out of 12 are dominant and 4 recessive to their wild-type alleles. One mutant,fpa60, showed a partial requirement for tyrosine and was found to be allelic to anfpaAmutant described previously. A tyrosine non-requirer,fpa65, was also assigned to this locus. The other 10 mutants did not show any growth requirement and were simultaneously resistant to ethionine and 3-amino-L-tyrosine. Of the 8 dominant mutants, 3 were allelic to the permease-mutants at the locusfpaD.Dominant mutants showed higher degrees of resistance than recessive ones. Six new loci, identified after preliminary genetic analysis, were located on 3 linkage groups: 3 on linkage group VI, and one each on linkage groups I, V, and VIII. The recombinantfpaD11;fpaK69 was found to be sensitive to FPA.
Nuclear and cytoplasmic cross-resistance and correlated sensitivity to DNA intercalating drugs in a petite-negative yeast
Authors: Celis Esteban , Mas Jaime , Brunner Aurora 
Published: September 2009

SUMMARYEthidium bromide and acriflavin-resistant mutants of petite-negative yeastKluyveromyces lactiswere prepared. One kind of nuclear mutation (EBR1) gave resistance to ethidium bromide and correlated sensitivity towards acriflavin. Another nuclear mutation (EBR2) did not affect ‘natural’ resistance of this yeast towards 15 μM acriflavin. Both nuclear mutations mapped at differentloci, suggesting lack of linkage. Cytoplasmic mutants resistant to these two drugs were unstable when grown in complete media with dextrose, reverting to a wild-type resistance genotype. When grown in glycerol-containing media these mutants maintained their cytoplasmic drug-resistance conferring factors.
On sojourn times at particular gene frequencies
Authors: Pollak Edward , Arnold Barry C. 
Published: September 2009

SUMMARYThe distribution of visits to a particular gene frequency in a finite population of sizeNwith non-overlapping generations is derived. It is shown, by using well-known results from the theory of finite Markov chains, that all such distributions are geometric, with parameters dependent only on the set ofbij's, wherebijis the mean number of visits to frequencyj/2N, given initial frequencyi/2N. The variance of such a distribution does not agree with the value suggested by the diffusion method. An improved approximation is derived.
Chromosomal location of prophage J51 inPseudomonas aeruginosastrain PAO
Authors: Carey K. E. , Krishnapillai V. 
Published: September 2009

SUMMARYThe UV-inducible prophage J51 has been mapped late on the chromosome ofP. aeruginosastrain PAO, relative to the entry point of the sex factor FP2. This was determined following the analysis of the segregation of unselected markers in conjugational crosses between appropriately marked donor and recipient strains. A more precise location of about 50 min was obtained from the kinetics of increase in infectious centres due to zygotic induction during interrupted mating experiments.
Evidence that Linkage Group IV as well as Linkage Group X of the mouse are in chromosome 10
Authors: Cacheiro N. L. A. , Russell Liane B. 
Published: September 2009

SUMMARYFour translocations in which one breakpoint was known to be at or closely linked to the LGIV marker Steel, Sl, were studied in an attempt to identify cytologically the as yet unassigned Linkage Group IV of the mouse. The cytological results indicate that chromosome 10, which had previously been matched with LGX, is involved in each of the four translocations, the break being in 10D. Recombination between Sl and the LGX marker grizzled, gr, was determined to be 6–14%. The combined cytological and genetic results indicate that LGIV and LGX are both in chromosome 10, and that the order may be centromere-gr-Sl.
An experiment on recombination load inDrosophila melanogaster
Authors: Charlesworth Brian , Charlesworth Deborah 
Published: September 2009

SUMMARYThis paper describes the results of an experiment to measure the effect on mean population fitness of recombination in the second chromosome ofDrosophila melanogaster. There was a small and non-significant effect of recombination in lowering egg-to-adult viability of heterozygotes for wild-type chromosomes. A large (7%) and significant effect of recombinant chromosomes on the fecundity ofCyfemale carriers was detected.
Properties of the R factor R144drd3 inKlebsiella pneumoniaestrain M5a1
Authors: Dixon R. , Cannon F. C. , Postgate J. R. 
Published: September 2009

SUMMARYThe R factor, R144drd3, mobilized chromosomal genes inKlebsiella pneumoniaestrain M5a1 at similar frequencies to those observed for this R factor inEscherichia coliK12. In a derivativeK. pneumoniaedonor, strain HF3, R144 persisted in the autonomous state but now gave rise to polarized transfer of the chromosome in the order Ohis…arg2…leu…trp. R144drd3 was unstable inK. pneumoniaeM5a1; after successive subculture drug resistance, colicinogeny and transmissibility were lost. In strain HF3, transmissibility was preferentially lost, but determinants for drug resistance, colicinogeny and superinfection immunity were retained; 10–11 copies per chromosome of R144 were present in log phase cultures of both strains.
Probability of identical monomorphism in related species
Authors: Nei Masatoshi , Li Wen-Hsiung 
Published: September 2009

SUMMARYA mathematical method for evaluating the probability that a locus is monomorphic for the same allele in related species is developed under the neutral mutation hypothesis. A formula for the proportion of identically monomorphic loci in related species is also worked out. The results of the application of this method toDrosophiladata do not support Prakash & Lewontin's (1968) contention that the strong association between gene arrangements (inversion chromosomes) and alleles at protein loci is evidence of coadaptation of genes in the inverted segment of chromosomes. Similarly, unlike Haigh & Maynard Smith's (1972) contention, the monomorphism of the haemoglobin α chain locus in man can be accommodated with the neutral mutation hypothesis without invoking the bottleneck effect.
Alcohol dehydrogenase activity inDrosophila melanogaster: a quantitative character
Authors: Ward R. D. 
Published: September 2009

SUMMARYAlcohol dehydrogenase activity inDrosophila melanogastermay be considered as a quantitative character, since it shows many features typically associated with such traits. Although strains with the electrophoretically fast phenotype generally have activities greater than those with the slow phenotype, presumably reflecting differences in the nucleotide sequences of the structural alleles, within each electrophoretic class there is considerable variation in activity. The expression of the structural gene, in terms of ADH activity, is to some extent regulated by its genetic background. Strains homozygous for particular structural alleles respond to divergent directional selection for ADH activity. Modifiers have been located to theX, second and third chromosomes.
Observations on a set of radiation-induced dominantT-like mutations in the mouse
Authors: Bennett Dorothea , Dunn L. C. , Spiegelman Martha , Artzt Karen , Cookingham Janice , Schermerhorn Elizabeth 
Published: September 2009

SUMMARYGenetic analysis of seven dominant short tailed mutations independently induced by radiation of male mice showed that six were allelic toT(Brachyury) but not identical to it. Homozygotes for each mutant die at least 2 days earlier thanT/Thomozygotes; two that were studied histologically are indistinguishable from one another. The development of these abnormal embryos is arrested by seven days of gestation, when cells of embryonic ectoderm cease proliferation and become pycnotic. Endoderm and extra-embryonic ectoderm do not seem to be primarily affected, and survive and grow for at least 2 days more. Serological studies of one of these mutations suggest that it is a deletion. A review is presented of these and otherT-like mutations that have been described; from this it appears that five different categories ofT-like mutants are discernible.
Efficient curing of anEscherichia coliF-prime plasmid by phenothiazines
Authors: Mándi Y. , Molnár J. , Holland I. B. , Béládi I. 
Published: September 2009

SUMMARYChlorpromazine and several other phenothiazines at sub-bacteriocidal concentrations were found to cure anEscherichia coliF′lac+strain of its plasmid efficiently. Curing was most efficient at high pH and in complex medium when 70% or more of the bacteria were plasmid-free after 24 h growth of cultures in the presence of the drug.
The effects of temperature on aberrant ascus frequencies at theBufflocus inSordaria brevicollis
Authors: Ahmad A. F. 
Published: September 2009

SUMMARYSingle-point crosses using five allelic spore colour mutants at thebufflocus were carried out at different temperatures. The data suggest (i) that fixed or preferred opening points in the DNA, required for initiation of recombination events, are available more often at higher than at lower temperatures, (ii) opening points at or beyond both proximal and distal ends of thebufflocus respond similarly to variations in temperature, and (iii) the correction pattern seems to be independent of temperature at thebufflocus inS. brevicollis.
Biochemical characterization and genetic mapping of purine genes inMicrococcus luteus
Authors: Mohapatra Nirupama , Kloos Wesley E. 
Published: September 2009

SUMMARYPurine auxotrophs ofMicrococcus luteuswere induced byN-methyl-N′-nitro-N-nitrosoguanidine. They were biochemically characterized by growth stimulation with CO2-enriched air and purine intermediates and by the Bratton-Marshall test that is used to detect accumulated diazotizable amines. The mutants were divided into four classes:pur(EC),purH,purJ, andPur−. Thepur(EC) class was further subdivided intopurEandpurCby results of crossing all thepur(EC) mutants with a knownpurEreference strain (ATCC 27141). Mutants which were not linked to the referencepurEmarker were considered to bepurC. Genetic mapping was accomplished by using two-point reciprocal transformation crosses. The result of this study indicates thatpurJmutants may be loosely linked topurEandpurC, and purH mutants are not linked topurE,purCorpurJ.
Crossing over between closely linked markers spanning the centromere of chromosome 3 inDrosophila melanogaster
Authors: Sinclair Donald A. 
Published: September 2009

SUMMARYRecombination in a short genetic interval spanning the proximal region of chromosome 3 was studied in the regionsst-in-ri-eg2-Ki-pp. Crossover frequencies in this region varied considerably in different genetic backgrounds; however, in all genotypes, the following observations were made: (1) an excess of multiple recombinant chromosomes indicative of high negative interference, was detected; (2) among the multiple recombi-nants, a positive correlation of simultaneous exchange in the most proximal and shortest adjacent genetic intervals was noted; (3) several classes of reciprocal products were not equally recovered. Three possible explanations for these results are: pre-meiotic exchange, chromatid interference and gene conversion.
The genetic locations oftraO, finPandtra-4 on theE. coliK12 sex factor F
Authors: Willetts Neil , Maule John , McIntire Sarah 
Published: September 2009

SUMMARYUsing a series of Hfr and F prime deletion strains, the F transfer inhibition genefinPhas been mapped betweenoriandtraJ. Marker rescue experiments with the Hfr deletion strains further showed thattraO, the site of action of the transfer inhibitor, is located immediately to the left of, or possibly within,traJ, and that the polar mutationtra-4lies intraK.
Mapping the adrenal lipid depletion gene of the AKR/J mouse strain
Authors: Taylor B. A. , Meier H. 
Published: September 2009

SUMMARYThe pattern of inheritance of the autosomal recessive adrenal lipid depletion (ald) allele among the AKXL recombinant inbred mouse lines, derived from a cross between AKR/J and C57L/J, revealed that thealdlocus is located on chromosome 1 near the dipeptidase-1 (Dip-1) locus. The linkage was confirmed in a backcross generation and the gene orderln-Dip-1-aldwas established.
Relative retention of mitochondrial markers in petite mutants: mitochondrially determined differences betweenRHO(+) strains
Authors: Molloy P. L. , Linnane Anthony W. , Lukins H. B. 
Published: September 2009

SUMMARYThe relative frequency of retention of two mitochondrial loci, determining resistance to oligomycin (oli1) and erythromycin (ery1), has been analysed in petite (rho(−)) mutants derived from a number of unrelated strains ofSaccharomyces cerevisiae. The frequency of retention of one marker relative to the other in spontaneous petites showed marked variation dependent on the strain of origin. The differences between strains in this characteristic were shown to be mitochondrially determined. Further, for individual strains, the relative retention of the markers in petites derived after UV-irradiation varied considerably in several cases from that observed with spontaneous petites. The observations on relative marker retention and the varied effects of UV-irradiation are discussed in terms of possible structural differences in the mitochondrial genomes of the various strains.
Mapping an invisible lethal in the mouse
Authors: Wallace Margaret E. 
Published: September 2009

SUMMARYAn effective breeding policy is described for detecting linkage in the mouse, for an ante-natal lethal from crosses of heterozygotes with stocks homozygous for several linked recessive markers. A method of analysing the ensuing data is described, together with a method of estimating the map distance to close markers. A practical illustration is described, involving an ante-natal lethal obtained from a colony of wild mice and a four fold recessive chromosome 2 marker stock.
Ovulation rate of lines of mice selected for testis weight
Authors: Mafizul Islam A. B. M. , Hill W. G. , Land R. B. 
Published: September 2009

SUMMARYSelection was practised in two replicates for both high and low testis weight in the mouse. Typically 7 males were selected out of 30 recorded for a total of 5 generations. From an initial average of 191 mg the mean divergence between high and low lines reached 112 mg, with a realized heritability of 0·52. The ovulation rate of the lines changed in the same direction as that of selection, the mean divergence was 2·0 eggs in primiparous females in generation 4 and 1·6 in nulliparous females in generation 5. Correlated changes in the body weight of both sexes also occurred but were inadequate to account for the observed change in ovulation rate. The genetic regressions of ovulation rate on testis weight were estimated to be 2·9 and 14 eggs/100 mg in primiparous and nulliparous females, respectively, which, along with data from other experiments, correspond to genetic correlations between testis weight and ovulation rate of 0·50 and 0·25 respectively. There were no correlated changes in litter size. The possibility of using male testis size in breeding programmes to improve female reproductive performance is discussed.
Genetics of plate morphology in an unusual population of threespine sticklebacks (Gasterosteus aculeatus)
Authors: Avise John C. 
Published: September 2009

SUMMARYA collection ofGasterosteus aculeatusfrom a single locality (Friant) in Madera County, California, contains individuals with low and high lateral plate morphology, and very few intermediates. Electrophoretic evidence on protein similarities at 15 genetic loci is compatible with the thesis that members of these two morphs belong to a single interbreeding population. This thesis is also supported by broods from laboratory crosses between morphs, which segregate for low and high plate counts. Laboratory crosses between Friant fish and those from geographically isolated populations often yield some progeny with intermediate plate counts. The demonstration of significantly different patterns of plate development in intralocality versus interlocality crosses evidences a contrasting genetic basis for plate determination in different populations of sticklebacks.
The incidence of chromosomally unbalanced gametes in T(14; 15)6 Ca heterozygote mice
Authors: Kaufman M. H. 
Published: September 2009

SUMMARYWhen T6/+ female mice were mated to non-translocation-bearing males, the relative viability of the embryos at 13·5–14·5 days gestation was about 39%. About 36% of the oocytes ovulated by T6/+ females were aneuploid, as a result of non-disjunction at meiosis, the majority having either 19 or 21 chromosomes. However, aneuploidy only accounts for a proportion of the embryonic loss in T6/+ × +/+ matings, as many of the embryos with 41 chromosomes survive postnatally. The present findings indicate that approximately 50% of the oocytes ovulated with the normal haploid number of chromosomes (n= 20) were genetically unbalanced as a result of adjacent segregation, and that a high proportion of the resultant embryos die in the early postimplantation period. In the present study non-translocation-bearing mice which were genotypically similar to the T6/+ females acted as controls.
Selection and analysis of a mutantParamecium tetraurelialacking behavioural response to tetraethylammonium
Authors: Chang Sheng-Yung , Kung Ching 
Published: September 2009

SUMMARYWe selected a mutantParamecium tetraureliawhich does not exhibit avoiding reaction in solutions of tetraethylammonium (TEA+), a known membrane K+-channel blocker. Behavioural reaction of the mutant to Na+solutions was also weak. The rapid successions of avoiding reactions in Ba2+solutions were observed in both wild type and the TEA-insensitive mutant. Formal genetic analyses showed that this mutant is due to a recessive mutation. This mutation is on a gene completely unlinked to and hypostatic in different degrees to the genes for the membrane defects of ‘pawn A’, ‘pawn B’, ‘ts-pawn C’, ‘fast-2’ and ‘paranoiac A’.