bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gamones and mating types in the genusBlepharismaand their possible taxonomic application
Authors: Miyake Akio , Bleyman Lea K. 
Published: September 2009

SUMMARYMating types I and II ofBlepharisma japonicum v. intermediumexcrete gamones 1 (blepharmone J) and 2 (blepharismone) respectively. The gamone of one type transforms cells of the other type so that they can conjugate with each other. We found that three other species,B. americanum, B. musculusandB. stoltei, have two types of cells homologous to those inB. japonicum; one (type II) excretes a factor which has the same activity as gamone 2 ofB. japonicum, the other (type I) responds to this gamone by cell union. Type I cells of these species also excrete a gamone which induces pairs in type II cells of particular strains. Complementarity for mating is observed in some combinations of the two types.These results indicate that each of the four species has at least one pair of complementary mating types, I and II, with the gamones of the type II's being the same molecule, blepharismone, while gamones of type I's are species- or syngen-specific blepharmone. These generic and specific gamones can be utilized to clarify existing taxonomic and evolutionary questions in the genusBlepharisma.
Calcium chloride effects on nuclear development inTetrahymena
Authors: Nanney D. L. 
Published: September 2009

SUMMARYConjugating pairs of syngen 1 exposed to 0·1 M-CaCl2during the time of macronuclear development often abort the new macronuclei and retain the old macronucleus and its associated phenotypes. The new micro-nucleus is retained, however, so that macro–micro heterocaryons can be constructed. Because the macronucleus is from a sexually mature strain, the heterocaryon is capable of mating immediately, without passing a period of sexual immaturity. Macronuclear abortion may prove a useful short-cut in genetic analysis.
Male meiotic behaviour and male and female litter size in mice with the T(2; 8)26H and T(1; 13)70H reciprocal translocations
Authors: de Boer P. 
Published: September 2009

SUMMARYTwo reciprocal mouse translocations T(2; 8)26H and T(1; 13)70H, heterozygous in a Swiss random-bred background, show differences in the spectrum of multivalent configurations and in the segregational behaviour of these multivalent configurations. T26H/+ males mostly contained rings of four (R IV, 53·15%) and T70H/+ males chains of four, missing a chiasma in the shortest interstitial segment (C IV 11, 61·55%). The adjacent II frequency, estimated from metaphase II observations, was 8·47% in T26H/+ and 25·22% in T70H/+. Univalents of the shorter translocation chromosome of T70H are able to divide equationally at first anaphase. The hypothesis is advanced that time differences in chiasma terminalization during metaphase I-anaphase are important for explaining the difference in segregation observed between the two translocations. Translocation-caused non-disjunction is probably low in T26H/+ and 4–5% in T70H/+. Univalents involving T70H/+ are usually capable of co-orientation with the other chromosomes of the translocation complex. The summed percentages of adjacent II disjunction and non-disjunction caused by the translocations were estimated from the relative fertility scores of T/+ males and females versus +/+ males and females as 9·8% and 29·0% for T26H/+ and T70H/+ males, respectively, and 9·4% and 27·8% for T26H/+ females and T70H/+ females. For both translocations, the agreement between the various estimates is good. Chiasma frequencies are much higher in telomeric segments than in proximal segments containing centric heterochromatin.
The effect of aneuploidy on meiotic crossing over and segregation in yeast
Authors: Duck P. , James A. P. 
Published: September 2009

SUMMARYMeiotic chromosome associations in homothallic strains ofS. cerevisiaewere investigated by analysis of meiotic spore colonies and crossing over in +/+/− trisomics. The segregants of these aneuploids produce phenotypically distinguishable tetrasomic spore colonies. The data indicate that trivalent associations occur with a high frequency in trisomics of chromosome XVII and that the frequency of second division segregation is markedly increased over that found in the normal dipoid.
The effect of selection on genetic variability: a simulation study
Authors: Bulmer M. G. 
Published: September 2009

SUMMARYComputer simulations have been done to study the effects of stabilizing and disruptive selection on a polygenic character. The results are reported in terms of three components of genetic variability which represent changes in gene frequencies, departures from Hardy–Weinberg equilibrium and linkage disequilibrium respectively. Under random mating the first and third components are the most important. The observed changes in gene frequencies are interpreted in the light of previous theoretical work on the stability of equilibria under selection. In addition, large and rapid changes in the genotypic variance result from the generation of linkage disequilibrium under selection; the observed changes are in good agreement with those predicted on theoretical grounds.
Development ofDrosophilaon sterol mutants of the yeastSaccharomyces cerevisiae
Authors: Bos Marten , Burnet Barrie , Farrow Roy , Woods Robin A. 
Published: September 2009

SUMMARYFour species ofDrosophila (melanogaster, simulans, mauritianaandvirilis) were tested for their ability to survive onergstrains ofSaccharomyces cerevisiaeeach having a mutant block at a different reaction in the synthesis of ergosterol. Species capable of completing development on a given yeast mutant strain were tested for egg production and viability, and also for their ability to survive on the mutant yeast for five complete generations. Sterol analyses using gas–liquid chromatography show that the sterol composition of flies closely resembles that of the yeasts on which they are grown, confirming that the steric criteria for sterols capable of a structural role in lipoprotein membranes are relatively broad. Even so, different sterols are not equally efficient in this respect and there are differences between species in their tolerance to the sterols available from each of the yeast mutants. The range of sterols capable of satisfying the micronutrient, as distinct from the macronutrient, requirement is narrower. Growth on two of the yeast mutants (erg-2anderg-6) leads to developmental arrest in the larval stage due, it is suggested, to a block in the synthesis of ecdysone. The fourDrosophilaspecies lack an effective level of Δ8−Δ7isomerase which is necessary for utilization of zymosterol and other Δ8sterol precursors of ergosterol. Ergosta-5,7-diene-3β-ol appears to be capable of substituting for cholesterol in the metabolism ofDrosophila.
The transient distribution of allele frequencies under mutation pressure
Authors: Nei Masatoshi , Li Wen-Hsiung 
Published: September 2009

SUMMARYThe transient distribution of allele frequencies in a finite population is derived under the assumption that there arekpossible alleic states at a locus and mutation occurs in all directions. At steady state this distribution becomes identical with the distribution obtained by Wright, Kimura and Crow whenk= ∞. The rate of approach to the steady state distribution is generally very slow, the asymptotic rate being 2v+ 1/(2N), wherevandNare the mutation rate and effective population size, respectively. Using this distribution it is shown that when population size is suddenly increased, the expected number of alleles increases more rapidly than the expected heterozygosity. Implications of the present study on testing hypotheses for the maintenance of genetic variability in populations are discussed.
The combinations of the sexes in twin lambings
Authors: James William H. 
Published: September 2009

SUMMARYEvidence is presented that the distribution of the combinations of the sexes in twin lambings has subnormal dispersion: there are more opposite-sexed pairs than same-sexed pairs. When adjustment is made for the occasional presence of monozygotic twin pairs, the departure from expectation (on the assumption that the sexes of DZ twins are distributed binomially) is highly significant. Thus sheep litters seem to show a feature characteristic of litters of pigs and (probably) mice and rabbits. This is consistent with the suggestion that p, the probability of a male zygote, varies systematically from one zygote to another within a litter.
RP4 Fertility Variants inAcinetobacter calcoaceticus
Authors: Towner K. J. , Vivian A. 
Published: September 2009

SUMMARYThe resistance plasmid RP4 can be used to mediate conjugation inAcinetobacter calcoaceticus. Transfer of chromosomal genes occurs only on solid surfaces and not in liquid matings. Two RP4-carrying donor strains which donate the chromosome in different directions from different origins have been isolated. As a result it is possible to demonstrate that the linkage map ofA. calcoaceticusis circular.The fate of RP4 in recombinants was examined. Although frequent loss of the complete plasmid was detected, segregation of plasmid antibiotic resistances was not observed.A possible mechanism by which RP4 could interact with theA. calcoaceticuschromosome is discussed.
Isolation and Analysis of Amoebal–Plasmodial Transition Mutants in the MyxomycetePhysarum polycephalum
Authors: Anderson R. W. , Dee Jennifer 
Published: September 2009

SUMMARYPlasmodium formation in the MyxomycetePhysarum polycephalumnormally involves fusion of haploid amoebae, carrying different alleles at the mating type (mt) locus, to give diploid plasmodia. Strains carrying themthallele are capable of undergoing the amoebal–plasmodial transition with high efficiency within amoebal clones, resulting in the formation of haploid plasmodia. NMG mutagenesis ofmthamoebae, followed by an enrichment procedure, was used to isolate mutants in which such clonal plasmodium formation was either delayed or absent. Thirteen mutants of the second type were analysed. Three of these were temperature-sensitive for plasmodium formation. All thirteen mutants were able to form diploid crossed plasmodia when mixed with amt1strain. Three new genes were identified and designatednpfA,npfB andnpfC. A mutant allele ofnpfA renderedclonalplasmodium formation temperature-sensitive, but did not prevent crossing at the non-permissive temperature with derived strains carrying the same mutant allele. No recombination was detected betweennpfB ornpfC andmt, butnpfA was unlinked tomtand a locus (apt-1) shown in a previous study to be involved in plasmodium formation. The genesnpfB andnpfC were distinguished by complementation analysis. Strains of the genotypenpfB−;npfC+behaved in the same way as strains carrying themt2allele. The nature of the mutants and the role of the mating-type locus in the initiation of plasmodium formation are discussed.
Mutagen specificity in conversion pattern inSordaria brevicollis
Authors: Yu-Sun C. C. , Wickramaratne M. R. T. , Whitehouse H. L. K. 
Published: September 2009

SUMMARYA total of 39 mutants at thegrey-3,grey-4andgrey-5spore colour loci inSordaria brevicollishave been investigated for conversion pattern by crossing them with wild type and counting aberrant asci. Twenty-one of the mutants were obtained with ICR170 and all showed postmeiotic segregation only rarely (0–8% of the aberrant asci); two showed conversion predominantly to wild type (class A) and the other 19 predominantly to mutant (class B). Six mutants were obtained with ethylmethane sulphonate and one with nitrosoguanidine, and they all showed postmeiotic segregation frequently (14–54% of the aberrant asci) and conversion usually about equally frequently in each direction, though with considerable diversity between mutants (class C). Eleven UV-induced mutants comprised one of class B and ten of class C. There was considerable variation in aberrant ascus frequency between alleles, but conversion pattern seemed to be independent of this frequency.
Variability in genetic parameters among small populations
Authors: Avery P. J. , Hill W. G. 
Published: September 2009

SUMMARYFor a model in which quantitative traits are assumed to be determined solely by additive genes at many loci, formulae are developed for the variance among replicated small populations of sizeN, maintained without selection, of the additive genetic variance, heritability, genetic correlations and similar parameters. The base population is assumed to be in linkage equilibrium, but it is argued that most of the variation in the within-line additive variance (VAtat generationt) is due to linkage disequilibrium caused by sampling. Ifis the squared correlation of gene frequencies averaged over all pairs of loci at timet, the coefficient of variation (CV) ofVAtequals, with similar formulae for other parameters.The formulae are evaluated for models of loci distributed uniformly along the chromosome but much of the disequilibrium is due to loci on different chromosomes. For unlinked loci CV(VAt) reaches √4/(3(N)), and for mammalian models, this value is not greatly exceeded. The variance in successive generations has a correlation of at least one-half due to the maintenance of linkage disequilibrium. The magnitude of this variance in parameters and their autocorrelation with time shows that accurate predictions cannot be made about genetic parameters in the base population from single replicate results.
Studies on male recombination in a Southern GreekDrosophila melanogasterpopulation: (a) Effect of temperature. (b) Suppression of male recombination in reciprocal crosses
Authors: Yannopoulos George , Pelecanos Michael 
Published: September 2009

SUMMARYA second chromosome ofDrosophila melanogaster(symbol 31.1) isolated from a natural population of North-Western Peloponnesus (at a distance of 8 km from the city of Patras) was found to induce recombination in heterozygous males, both in the second and third chromosomes. The present study also revealed the following points. (1) The phenomenon is temperature-sensitive with higher male recombination at 29 °C than at 25 or 15 °C. (2) The temperature-sensitive period is during the larval stage where premeiotic divisions of germ cells take place. (3) Suppression of male recombination in both the second and third chromosomes occurred when 31.1/CyL4females were used in the matings, and (4) the suppression of male recombination is caused by a cytoplasmic factor of theCyL4/Pmstock.
Selection oflonmutants inEscherichia coliby treatment with phenothiazines
Authors: Molnár J. , Holland I. B. , Mándi Yvette 
Published: September 2009

SUMMARYGrowth ofE. coliK12 in the presence of chlorpromazine or promethazine resulted in the appearance of a special kind of mutational change with a frequency of 5–10%. These cells were UV-sensitive and very mucoid in their colony formation. The strains were characterized as colanic acid producing on the basis of phage m-59 sensitivity and we tentatively conclude that these mutants are Lon−.In another series of experiments drug treatment ofE. colifailed to yield significant numbers of auxotrophs and the back mutation rate of a number ofS. typhimuriumHis−strains was not significantly increased.
Reciprocal differences in female recombination associated with hybrid dysgenesis inDrosophila Melanogaster
Authors: Kidwell Margaret Gale 
Published: September 2009

SUMMARYLarge reciprocal differences in recombination frequencies were observed in F1female progeny of a number of strain crosses. These reciprocal effects on recombination were found in several intervals of all three major chromosomes; they were greatest in intervals proximal to or spanning the centromere but were also found in some distal regions. The direction of recombination change was not consistent over different chromosomal intervals. There was no clear trend for reciprocal recombination differences to be associated with change of interference values between adjacent intervals. A close association was found between reciprocal female recombination effects, male recombination and other component traits of hybrid dysgenesis. However, reciprocal differences in female recombination were not restricted to dysgenic crosses. Backcross experiments demonstrated that reciprocal differences in the centromeric region of chromosome III were the result of increased crossing-over in dysgenic F1 hybrids rather than decreased crossing-over in the reciprocal hybrids. It is concluded that genotype-cytoplasm interaction can be a major factor influencing recombination frequencies and that the use of interstrain hybrids for recombination measurement may lead to errors in the estimation of intrastrain frequencies.
Associations between allozyme loci and gene arrangements due to hitch-hiking effects of new inversions
Authors: Ishii K. , Charlesworth B. 
Published: September 2009

SUMMARYThis paper examines the hypothesis that the associations between alleles at allozyme loci and gene arrangements, which are observed in many Drosophila populations, result from inversions remaining associated with the alleles contained in the gametes in which they originally occurred. The effects of double crossing over in heterokaryotypes and of selection at loci linked to the allozyme loci, which are themselves assumed to be neutral, are studied theoretically. It is concluded that selection at linked loci is unlikely to have an important effect in retarding the decay of this type of association. The literature on associations between allozymes and gene arrangements is surveyed, and it is concluded that a ‘neutralist’ explanation of this sort cannot be excluded, except possibly in some cases where the allozyme locus is outside the inversion breakpoints and crosses over with measurable frequency in heterokaryotypes.
Sterile mutation inDrosophila melanogaster
Authors: Watanabe Takao K. , Lee Won Ho 
Published: September 2009

SUMMARYThe number of loci which are potentially able to produce sterility genes was estimated forDrosophila melanogaster. There appear to be, on the second chromosome, about 80 loci capable of producing male sterility and about 60 loci capable of producing female sterility. These figures seem to be considerably less than (400–500) loci responsible for lethal genes.
Digenic descent measures for finite populations
Authors: Cockerham C. Clark , Weir B. S. 
Published: September 2009

SUMMARYThe development of a set of two-locus descent measures is reviewed. The three digenic measures, inbreeding coefficient and parental and recombinant descent coefficients, are considered in detail. The derivations of these three in pedigrees, fixed mating systems, and random mating in monoecious or dioecious populations are given. General expressions for digenic frequencies and disequilibria functions at any time are found by applying the three digenic descent measures to two types of initial populations. The final or equilibrium status of the population is also given. As the inbreeding coefficient is the same as the recombinant descent coefficient in the case of complete linkage, avoidance or promotion of early inbreeding has similar effects on the two coefficients. Estimable components of linkage disequilibrium and other measures of association within and among populations are elaborated.
The basis for an apparent auxotrophy for reduced sulphur metabolites insF−mutants ofAspergillus nidulans
Authors: Arst Herbert N. 
Published: September 2009

SUMMARYsF−mutants ofAspergillus nidulansare subject to toxicity by a metabolite derived from sulphate but are not blocked in cysteine biosynthesis. Bearing in mind the unavoidable presence of sulphate in agar-solidified media, their apparent auxotrophy for thiosulphate, L-cysteine or L-methionine stems from the ability of these reduced sulphur-containing metabolites to repress, directly or indirectly, the syntheses of sulphate permease and the enzymes of sulphate assimilation, thereby preventing synthesis of the toxic metabolite.
Genetic latitudinal adaptation ofDrosophila melanogaster: new discriminative biometrical traits between European and equatorial African populations
Authors: David J. , Bocquet C. , de Scheemaeker-Louis M. 
Published: September 2009

SUMMARYFive biometrical traits (thorax length, wing length and width, sternopleural and abdominal chaetae numbers) were measured on 13 equatorial African strains and 30 French strains. In all cases highly significant differences were observed between the two geographic groups. These results are added to previously known variations concerning adult weight and ovariole number. In each place, the genetic particularities of the wild populations seem to be maintained by the selective pressure from environmental conditions, resulting in a homeostatic focusing of the best fitted average genotype. Analysis within each group showed that variations between strains were in most cases poorly or not correlated, so that partial or total genetic independence between the various traits measured seems likely.
Fine structure mapping and properties of mutations suppressing thelonmutation inEscherichia coliK-12 and B strains
Authors: Johnson Ben F. 
Published: September 2009

SUMMARYMutations,sulAandsulB, that suppress the UV sensitivity conferred by thelonmutation have been isolated and precisely positioned on the linkage map ofEscherichia coli. TheE. coliB strains Bs-3 and Bs-8 have been shown to possesssulAmutations. Also theE. coliK12 strain J6271 that possesses a suppressor of thelonmutation, previously designated assuf, has been shown to be asulAmutation. A series of methylmethane sulphonate resistant derivatives of anE. coliK12lonstrain has been isolated and genetically characterized. In addition tosulAmutations, a second suppressorsulBwas identified and located betweenleuandazigenes on the chromosome. NeithersulAorsulBmutations result in increased sensitivity to the antibiotics ampicillin, rifampicin, or actinomyein D, nor do they have any significant effect upon the overproduction of mucopolysaccharide caused by thelonmutation. Under some growth conditions thesulBmutation causes cells to be temperature sensitive for the cell division process at 42 °C.
Studies on male recombination in a Southern GreekDrosophila melanogasterpopulation
Authors: Yannopoulos George 
Published: September 2009

SUMMARYA combined cytological and genetic analysis has been carried out to determine whether the spontaneous male recombination associated with a line ofDrosophila melanogasterderived from Southern Greece (31.1 MRF) involves chromosome breakage and random reunion. In all crosses showing male recombination, extensive abnormalities involving anaphase bridges and fragments were found at first and second meiotic divisions. This confirms that the low level of recombination associated with male recombination lines is not produced by normal, controlled crossing-over of the type found in females, but by chance reunions, following more erratic breakage events at first and second anaphase. In addition the occurrence of some limited premeiotic recombination cannot be excluded. The31.1 MRFsystem shows higher recombination levels at elevated temperatures (29 °C) and chromosome abnormality frequency is also greatly increased. The31.1 MRFinduces both male recombination and chromosomal abnormalities at meiosis when it is inherited from females deriving their cytoplasm from stock other thanCyL4/Pm. It is concluded that this factor acts independently of sex and that the reciprocal cross effect is caused by a cytoplasmic factor which the 31.1/CyL4strain inherited from theCyL4/Pmstock.