bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ovulation and post-ovulational losses in strains of mice selected from large and small litters
Authors: Bateman Nigel 
Published: September 2009

This paper describes the aspects of fertility that had been affected by selection on litter size. For twelve generations previously the mice used as parents were chosen because they had been born in large or small litters. At the end of this time, litters in the fertile strain averaged 11·1 young born alive, while the less fertile strain averaged 5·5.It was found that male fertility and inherent viability of the young had nothing to do with the response although neither was excluded by the method of selection. Several contributions, however, were made by the females, who were affected not only in ovulation rate, but also in their control of pre-implantational losses, foetal mortality and mortality of the newly born.Females from the less fertile strain were particularly prone to pre-implantational loss of eggs. It remains to be shown whether these were due to fertilizational or implantational failure.The incidence of earlier and later embroyonic losses in females of the same strain were uncorrelated—Utters that were depleted early were neither more nor less inclined to be depleted later.
Purification of argininosuccinase fromNeurosporaand comparison of some properties of the wild-type enzyme and an enzyme formed by inter-allelic complementation
Authors: Cohen Brian B. , Bishop John O. 
Published: September 2009

Argininosuccinase has been purified from wild-typeNeurospora crassa, strain ST.A. The purified enzyme, which is homogeneous by the criteria of analytical centrifugation and starch-gel electrophoresis, has a molecular weight of about 175,000. The enzyme has also been partially purified from a heterokaryon between thearg-10 mutant stocks B317–9–9aand 402–3a.The reaction kinetics of the two enzymes were compared in several respects, and they were found to be indistinguishable. The enzymes were also indistinguishable by starch-gel electrophoresis, and sedimented at the same rate through a sucrose gradient. It seems likely, however, that the enzymes do differ physically since they showed different affinities for both calcium phosphate gel and hydroxylapatite during purification.
Recombination within theamgene ofNeurospora crassa
Authors: Fincham J. R. S. , Pateman J. A. 
Published: September 2009

Maps have been made showing the order ofammutant sites using (a) frequencies ofam+recombinants from crosses betweenammutants and (b) the modes of distribution of theam+recombinants among the two parental and two recombinant classes with respect to the flanking markersinosandsp.It is possible to arrange the sites in an order such that, in almost all the crosses yielding useful numbers ofam+recombinants, thespallele originally in coupling with the distalammutant site occurs in the majority of the recombinants. No such consistent pattern was found with respect to theinosmarker. The order obtained by reference tospagreed with the best order deducible from recombination frequencies.The data are consistent with the hypothesis thatam+recombinants arise by a process of gene conversion, that there is a gradient of conversion frequencies from the right (inosor distal) end of the gene to the left (spor proximal) end, and that conversion tends to be associated (though less than 50% of the time) with crossing-over, especially on the distal side.There is no obvious relationship between the map position of a givenammutant and the properties of the protein product of the mutant gene.
Dilution of gene products in the cytoplasm of heterokaryons inCoprinus lagopus
Authors: Casselton Lorna A. , Lewis D. 
Published: September 2009

(a)Coprinus lagopushas in nature both a monokaryon with one haploid nucleus per cell and a dikaryon with two haploid nuclei per cell. It also has in experiment both a heterokaryon with two types of nuclei distributed irregularly in the mycelium and a diploid monokaryon with one diploid nucleus per cell.(b) Two pairs of linked recessive auxotrophic mutants,me-5ad-8 andadhis-1chol-1 have been combined in two different sets of multiple heterogenotes so that in the dikaryon and heterokaryon the + (active) alleles of the four genes are distributed equally in the two component nuclei. In one combination the linked genes are intransand in the other they are incisarrangement in diploid, dikaryon and heterokaryon.(c) Complementation between the + genes, as measured by growth on minimal and complete media, was complete in the diploid and dikaryon but was only partial in the heterokaryon.(d) A similar comparison of a recessive suppressor of the mutantme-1 revealed that the recessive gene was not expressed and therefore was fully recessive in the diploid and dikaryon but was only partially recessive in the heterokaryon.(e) The exact similarity of complementation of the structural genes of the auxotrophic mutants and the recessiveness of theme-1 suppressor in diploids and dikaryons exclude a localization of gene interaction in the nucleus. In a heterokaryon cytoplasmic dilution of the product of a dominant gene can occur and has the effect of producing a phenotypic difference between heterokaryons and diploids.
Genetic control of recombination and the incompatibility system inSchizophyllum commune
Authors: Simchen G. 
Published: September 2009

Crossing-over between the α and the β loci constituting theAincompatibility factor gives rise to two new specificities which are compatible with both parental As and with each other. The frequency of monokaryotic mycelia carrying re-combinant A factors is shown to be under genotypic control in a multiple crosses programme (6 × 6), selection for high and low recombination frequencies (two generations), and crosses between the selection lines. The recombination values based on samples of 100 monokaryons, range from 0 to 21%; however, the more accurately estimated values of the ‘High’ and ‘Low’ selections are 14% and 4%, each being based on approximately 2,000 mycelia.The data are compatible with a gene-system consisting of the postulated locusrecwhich has a major effect on recombination and which is linked to the A factor, and several minor effects by other loci. Alternative interpretations are presented and discussed. The apparent dominance of low frequencies of recombination on high frequencies can be related to the breeding behaviour ofS. commune.Thus close linkage between α and β allows a high number of A specificities to be maintained in a population as well as high out-breeding potential, while the inbreeding potential (i.e. dikaryotic combinations between monokaryons originating from a single fruit-body) is kept low and near its minimum.The significance of the two-locus structure of the incompatibility factors is examined theoretically in an Appendix at the end of the Discussion section.
Tests for an effect of the Y-chromosome on the mutagenic action of formaldehyde and X-rays in Drosophila melanogaster
Authors: Ratnayake Winston E. 
Published: September 2009

An additional Y-chromosome in either male or female did not have an influence on the mutagenic action of formaldehyde–food. It is concluded that the lack of response of female germs cells to this treatment is not due to lack of a Y-chromosome, and that the specific response of spermatocytes among germ cells is probably not due to the striking activity of the Y in these cells.Kershner's (1949) observation that the sex-linked lethal frequency in X-rayed males was significantly reduced by an additional Y-chromosome could not be confirmed.
The incorporation of alien disease resistance in wheat by genetic interference with the regulation of meiotic chromosome synapsis
Authors: Riley Ralph , Chapman Victor , Johnson Roy 
Published: September 2009

1. Triticum aestivum ssp. vulgare variety Chinese Spring (2n = 6x = 42) is susceptible to yellow rust caused by Puccinia striiformis while the wild annual grass Aegilops comosa (2n = 14) is resistant to all the physiologic races for which it has been tested.2. By a backcrossing programme initiated from Chinese Spring × Ae. comosa hybrids, using Chinese Spring as the recurrent parent, a line was isolated with a single chromosome of Ae. comosa, determining rust resistance, added to the full complement of Chinese Spring.3. The alien chromosome substituted with good genetic compensation only for the chromosomes of homoeologous group 2 of Chinese Spring. This demonstrated that the chromosome determining rust resistance is in homoeologous group 2. It was designated 2M since Ae. comosa has the M genome.4. In order to induce recombination between 2M and its wheat homoeologues, hybrids were made using Ae. speltoides which has the capacity to suppress the activity of chromosome 5B that normally prevents homoeologous synapsis. A backcrossing programme, using Chinese Spring as the recurrent parent, was reinitiated from the 29-chromosome hybrids carrying chromosome 2M and the haploid complements of Chinese Spring and Ae. speltoides.5. Selection was practised for rust resistance and ultimately a resistant plant with 42 chromosomes, that formed 21 bivalents at meiosis, was isolated. This plant was heterozygous for a dominant rust resistance allele (Yr8) derived from Ae. comosa. Homozygotes were isolated in its progeny and in this way the rust resistant breeder's variety, Compair, was established.6. Compair differs from Chinese Spring in its yellow rust resistance which was shown to be determined by a chromosome corresponding to 2D of Chinese Spring. This chromosome of Compair has the short arm, the centromere and a proximal segment of the long arm of chromosome 2M and a distal segment of the right arm of chromosome 2D. The modified chromosome, which is designated 2M/D, arose by homoeologous recombination in the Ae. speltoides hybrid or in the immediately succeeding backcross generations. Chromosome 2M/D carries the Yr8 gene in the proximal segment of the long arm derived from chromosome 2M.7. In hybrids between Compair and standard wheat varieties, chromosome 2M/D pairs regularly with chromosome 2D so that regular segregation of Yr8 can be expected and Compair treated like any other parental variety in wheat hybridization programmes.8. This work illustrates the way that homoeologous recombination can be induced and exploited both in cytogenetic analysis in wheat and in practical breeding work. The nature of the meiotic synapsis of chromosome 2M/D with its partial homologues raises questions concerning the means by which chromosome 5B influences the specificity of meiotic synapsis.
Environmental influences on puffing in the salivary gland chromosomes ofDrosophila melanogaster
Authors: Burnet Barrie , Hartmann-Goldstein Ingeborg 
Published: September 2009

SUMMARYThe sequence of development of salivary gland chromosome puffs inDrosophila melanogastercultured on live yeast and RNA-deficient medium has been studied in late larval and prepupal stages. Differences in puffing pattern between individuals cultured in the two environments are almost entirely due to shifts in the relative timing of puff development at specific chromosome sites. Detailed studies on the right arm of the second chromosome indicate that, at certain sites, puffing activity spreads to adjacent lettered subdivisions of the chromosome. There are differences in the extent of lateral spreading of activity into adjacent regions in the two environments which may be due to clustering of functionally related genes.
Duration of meiosis in barley
Authors: Bennett M. D. , Finch R. A. 
Published: September 2009

SUMMARYThe duration of meiosis and its stages has been estimated in Hordeum vulgare variety Sultan grown at 20·0 °C with continuous illumination. The results are in good agreement with a previous estimate of the duration of meiosis and some of its stages in barley. The duration in barley does not differ greatly from that predicted from the previously calculated regression of DNA amount on meiotic duration in diploid plant species. As in other cereal species, meiosis is comparatively short.
Improvement of litter size in a strain of mice at a selection limit
Authors: Falconer D. S. 
Published: September 2009

SUMMARYA strain of mice that had ceased to respond to selection for high litter size was inbred with continued selection. Depression of the mean proved the existence of residual genetic variance. Four lines survived the inbreeding, and one reached 20 generations with a mean equal to the original strain, thus disproving overdominance as a major cause of the residual variation. The four selected inbred lines were crossed and a new strain derived from the cross was maintained in parallel with the original strain. The new strain showed an improvement of 1·5 mice per litter over the original strain. Thus selection with inbreeding was able to achieve an advance beyond the limit attained by the original selection.The hypothesis that the residual variation was due to genes with simple dominance was tested by seeing if it could account for the observations with reasonable values of the relevant parameters. The improvement made by the inbreeding and crossing required the elimination of about 30 recessive genes with effects (homozygote difference) of 0·5 phenotypic standard deviations and gene frequencies of 0·2. Consideration of the mean levels of the selected inbred lines in conjunction with the rate of depression found on inbreeding without selection showed that the selection with inbreeding had eliminated about 75% of the segregating reces-sives. The number of genes contributing to the residual variance was therefore about 40. The additive variance generated by these genes was just consistent with the estimate of zero from the realized heritability. Consideration of the original selection showed that about half the genes could have been still segregating when the response ceased. The hypothesis therefore requires the number of genes in the base population to have been about 80. The number of genes required, though large, does not seem impossible, and the hypothesis of genes with simple dominance can account for all the observations.
A semi-automatic technique for conducting many bacterial matings concurrently
Authors: Achtman Mark 
Published: September 2009

SUMMARYA technique using microserological equipment is described whereby up to 144 quantitative interrupted bacterial matings may be performed concurrently. The technique is easy to use, accurate and reproducible, and eliminates the need for agar plates. However, it is only suitable for 40–42 °C matings and mating efficiency is approximately threefold lower than in test tubes.
Mutants ofAspergillus nidulansunable to use choline-0-sulphate
Authors: Arst Herbert N. 
Published: September 2009

SUMMARYMutants ofAspergillus nidulansunable to use either the choline moiety or the sulphate moiety of exogenous choline-0-sulphate have been selected. Choline-0-sulphate non-utilizing (csu) mutations have no other apparent pleiotropic effects, but it has not yet been established whether they lead to loss of choline sulphatase (and thus of the ability to utilize endogenously produced choline-0-sulphate) or to loss of a specific transport system for choline-0-sulphate or to loss of both.
Transduction mechanisms of bacteriophage ε15III. A new class of mutations affecting the conversion ofSalmonella anatumby bacteriophage ε15
Authors: Hedges R. W. 
Published: September 2009

SUMMARYSalmonella anatumlysogenized by a doubly mutant strain of bacteriophage εγshows a markedly rough colonial phenotype on tetrazolium agar. Mutants that abolish the roughness are reported.
An invariant property of a structured population
Authors: Maruyama Takeo 
Published: September 2009

SUMMARYConsidering a single mutant gene in a geographically subdivided finite population, it is shown that the average number of heterozygotes, due to this gene, that appear in the population before fixation or loss of this gene is equal to twice the total population number. This is invariant under the geographical structure of the population.
Pattern of neutral polymorphism in a geographically structured population
Authors: Kimura Motoo , Maruyama Takeo 
Published: September 2009

SUMMARYIn a two-dimensional stepping-stone model of finite size, if a pair of alleles happen to segregate in the whole population, marked local differentiation of gene frequencies can occur only if migration between colonies is sufficiently rare so thatNm< 1, whereNis the effective size of each colony andmis the rate at which each colony exchanges individuals with four surrounding colonies each generation. On the other hand, ifNm≥ 4, the whole population behaves as if it were panmictic and the allelic frequencies become uniform over the entire distribution range unless mutation is unusually high. Tendency toward local differentiation is much weaker in two-dimensional than in one-dimensional habitats.
The time course of recombinant production inStreptomyces coelicolor
Authors: Sermonti G. , Puglia A. Maria , Ficarra Giuseppina 
Published: September 2009

SUMMARYThe process leading to gene recombination can be interrupted in the filamentous bacteriaStreptomyces coelicolorby growing mixed cultures on cellophane disks lying on complete medium. The mycelium is harvested, broken, diluted and the broken hyphae plated at different time intervals. By this means some markers can be excluded from heteroclones or from recombinant progeny in early samples. The recombinant pattern clearly changes with time, with an increase of markers contributed to the recombinant progeny. In crosses between male (NF) and female (UF) strains, the maleness is the first donor trait to appear in the cells of the recipient parent. The fertility factor does not produce a transfer origin on the donor chromosomes; the donor contribution may extend on either side or on both sides of the factor which appears to be compulsory for zygote formation. The longer the time of contact between parental cells, the longer the segment of the donor chromosome contributing to the recombinant progeny. When spores are formed they contain almost exclusively recombinant nuclei derived from segregation processes.
Mutants ofCoprinus lagopusselected for resistance to 2-deoxy-D-glucose
Authors: Moore David , Stewart George R. 
Published: September 2009

SUMMARYThe glucose analogue 2-deoxy-D-glucose seriously inhibits the growth ofCoprimts lagopus. Following treatment withN-methyl-N′-nitro-N-nitrosoguanidine 388 resistant mutants were isolated. It is shown that the mutants isolated are probably allelic; they were phenotypically similar and no complementation was observed. The mutants were pleiotropic in the sense that although they were initially selected only for resistance to 2-deoxy-D-glucose they were found to be cross-resistant to both of the related analogues, sorbose and glucosamine. Furthermore, the mutants were unable to utilize fructose as a sole carbon source. It is demonstrated that the inability to utilize fructose results from a defect in sugar transport. The gene symbolftris proposed for this cistron and it is shown that though the gene is quite closely linked to its own centromere, it is unlinked to centromere markers of the six known linkage groups.
Isolation and properties of mutants of the FP2 sex factor ofPseudomonas aeruginosa
Authors: Stanisich Vilma A. 
Published: September 2009

SUMMARYTwo new types of mutants of the FP2 sex factor have been isolated in males ofP. aeruginosastrain PAT. Males harbouring FPd mutants are unable to mediate either sex factor or host chromosome transfer, although they retain the exclusion and precipitation characteristics of wild-type males. Males harbouring the FPs mutant apparently have an altered cell surface as indicated by their loss of precipitability, and although their donor properties are similar to those of wild-type males they show a slightly reduced conjugal fertility.A previously described sex factor mutant FP* (Stanisich & Holloway, 1972) can be transferred to males carrying either the FPs or FPd factors, and the heterozygous strains produced show restoration of wild-type properties, i.e. wild-type precipitation characteristics of the FPs mutants, and transferability of FPd mutants respectively. This suggests that the mutations of the FPs and FPd factors are recessive to the alleles carried by the FP* factor. The ability to produce such heterozygous strains supports the view that at least two copies of the FP2 factor occur in strain PAT males.
Genetic differences between populations ofDrosophila melanogasterfor a quantitative trait: I. Laboratory populations
Authors: López-Fanjul C. , Hill W. G. 
Published: September 2009

SUMMARYAn experiment was carried out to test whether two laboratory cage populations ofDrosophila melanogasterfrom different origins (Kaduna and Pacific) differed in the genes for sternopleural bristle number. The means, variances and heritabilities of the two populations and the synthetic formed from crosses between them were very similar.Selection for low bristle number was practised in small replicate lines, six of each pure population and nine of the synthetic. On average, Pacific responded to selection rather more rapidly than either Kaduna or the synthetic, but there was little difference in the limit achieved.Crosses between replicates within populations were made and selection continued, and these lines subsequently crossed between populations and reselected. Additional response was obtained by this procedure but the crosses between the replicates of the pure and synthetic populations attained similar selection limits.An analysis of effects of individual chromosomes from the selected lines on bristle number indicated that the contribution of each chromosome to total response was about the same in Pacific, Kaduna and the synthetic.It is concluded that differences in gene frequency, rather than the presence or absence of particular alleles, are mainly responsible for the differences observed between the populations.
Genetic recombination betweenKlebsiella pneumoniaeandEnterobacter aerogenes
Authors: Matsumoto Hideki 
Published: September 2009

SUMMARYIntergeneric recombination of chromosomal genes between strains ofKlebsiella pneumoniaeandEnterobacter aerogeneshas been observed. In these experiments a male strain ofK. pneumoniaeacted as donor andE. aerogenesacted as recipient. Closely linked genes were co-transferred with very high frequency, and transfer of a large fragment carrying several separated genes was not uncommon. Subcultures of a hybrid which had received a large fragment carrying five markers were tested for genetic stability; no spontaneous segregants were found among 34000 colonies tested. These results suggest that the transferred fragment had been integrated, and indicate the close genetic relationship betweenK. pneumoniaeandE. aerogenes. This is in agreement with their very similar biochemical properties.
Natural selection with varying selection coefficients – a haploid model
Authors: Gillespie J. H. 
Published: September 2009

SUMMARYIn this paper an exact treatment is given for the stochastic behaviour of the frequency of haploid genotypes in an infinite population when the absolute fitnesses of the two genotypes vary at random over generations. The main qualitative result from this treatment is that natural selection will favour that allele with the largest geometric mean fitness. A diffusion equation is derived whose solution is identical to the exact solution. The drift coefficient for this equation is of the form − μp(1 −p) + σ2(½ −p)p(l −p). This differs from the drift coefficient used in previous treatments of this problem and reduces the rate of quasi-fixation. Various waiting time problems are solved using this diffusion equation.