bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selection for recombination in a polygenic model
Authors: Smith J. Maynard 
Published: September 2009

SUMMARYNormalizing selection with a moving optimum can result in strong selection for increased recombination. This conclusion is based on computer simulation of an infinite, random-mating diploid population with additive, polygenic determination of the selected phenotype. There can also be selection for increased recombination with a fluctuating optimum, and with directional selection. These effects which arise in an infinite population appear to be large compared to the additional effects arising in a finite population because of the random generation of linkage disequilibrium.
Transformation inEscherichia coli: studies on the nature of donor DNA after uptake and integration
Authors: Hoekstra W. P. M. , Bergmans H. E. N. , Zuidweg E. M. 
Published: September 2009

SUMMARYChromosomalE. coliDNA appears to be sensitive towardsin vivoDNA restriction when transformed to a restrictiveE. colirecipient. It is therefore concluded that transforming chromosomal donor DNA is present in a double-stranded form immediately after uptake.Genetic analysis ofE. colitransformants, obtained with UV-irradiated donor DNA under conditions that exclude photorepair, show, especially in auvrBrecipient, loss of donor DNA information compared with the situation where DNA was not subjected to UV-irradiation. Similar conclusions were arrived at after genetic analysis of transductants obtained with UV-irradiated particles of the generalized transducing phage P1. The processing inE. coliof DNA after P1 transduction is thus similar to that of transforming DNA. The observations are discussed and a possible explanation based on single-stranded DNA integration is presented in detail.
Repair of double-strand breaks and lethal damage in DNA ofUstilago maydis
Authors: Leaper S. , Resnick M. A. , Holliday R. 
Published: September 2009

SUMMARYThe size of nuclear DNA from wild-typeUstilago maydiswas determined to be approximately 6·09 ± 0·3 × 108daltons from neutral sucrose gradient sedimentation analysis. Following exposure to ionizing radiation the nuclear DNA size was reduced due to the production of double-strand breaks in the DNA. These breaks were repaired when the irradiated cells were incubated in medium for at least one hour after irradiation. The repair was seen as a shift in the DNA profile from a low molecular weight region where the control DNA sedimented. Inhibition of protein synthesis by cycloheximide prevented this type of repair. Blocking protein synthesis also decreased the survival of irradiated wild-type cells but not radiation-sensitive mutants. Protein synthesis was necessary within the first one and a half hours after irradiation for the survival of wild-type cells to be unaffected. The results provide additional evidence for an inducible repair process inU. maydis.
Evidence for duplicate genes coding for 6-phosphogluconate dehydrogenase in rye
Authors: Rao I. Narayana , Rao M. V. Prabhakara 
Published: September 2009

SUMMARYThe 6-phosphogluconate dehydrogenase (6-PGD) E.C. no. 1.1.1.44, zymogram phenotypes of wheat–rye addition lines and triticale were determined. Genes involved in the production of 6-PGD were located on the long arms of C and F chromosomes of Imperial Rye and the long arms of II and IV chromosomes of King II rye. The results indicate that this enzyme is a dimer.
A study of pili onPseudomonas aeruginosa
Authors: Bradley David E. 
Published: September 2009

SUMMARYPseudomonas aeruginosacarries polar pili which act as receptors for RNA-containing bacteriophages. In order to confirm, that these pili were not involved in the transfer of the sex factor FP 2, eleven bacterial strains, both FP 2+and FP 2−, were examined in the electron microscope for the presence of pili and tested for sensitivity to the RNA phage PP7. Pili were found on all strains save one which was resistant to phage PP7. It was also found by electron microscopy that about 25 times more pili per cell were present after PP7 adsorption than before it. This result is discussed with reference to the pilus retraction theory, providing further evidence that some kinds of pili retract instead of acting as simple tubes for the transfer of genetic material. The strong supporting evidence provided by the infective processes of male-specific coliphages is discussed and compared to current knowledge ofP. aeruginosaRNA phages.It was also found that pili were present on the host strain for theP. aeruginosafilamentous phage Pf. Although similar in appearance to RNA phage pili, these differed in that they did not adsorb phage PP7. However, it seemed likely that they were receptors for Pf. A structural comparison is made betweenP. aeruginosapili andEscherichia coliF-pili. It is possible thatP. aeruginosapili could be coded for by a plasmid other than FP 2.
Population size and protein variation in man
Authors: Haigh John , Maynard Smith John 
Published: September 2009

SUMMARYThe ‘neutral mutation theory’ holds that most amino acid substitutions in evolution are selectively neutral. The known pattern of variation in human haemoglobins can only be made consistent with this theory if the human species has passed through a bottleneck of numbers in the recent past. If this theory is true, estimates of the necessary size and duration of this bottleneck can be made. A theory is developed which leads to an estimate ofYg, n, the number of alleles present in a population which arise betweengandngenerations ago, and hence to the estimatewhereuis the neutral mutation rate andNethe effective population size, for the probability that a population contains no such alleles. Using data on haemoglobins, this gives an approximate upper limit to the time elapsed since the bottleneck in human numbers. Either such a bottleneck occurred, or the neutral mutation theory is false; data on other proteins will enable a choice between these possibilities to be made.
Interspecific crosses and crossing-over inNeurospora
Authors: Newcombe K. D. , Threlkeld S. F. H. 
Published: September 2009

SUMMARYThrough a series of backcrosses the centromere region of linkage group I ofNeurospora crassawas transferred to theN. sitophilagenome, and through another series of backcrosses the centromere region of linkage group I ofN. sitophilawas transferred toN. crassa. Strains thus synthesized showed, in further crosses, that theN. sitophilacentromere region acts as a dominant enhancer of cross-over frequencies across linkage group I of the two species.
The effects of inversions and theC(3)Gmutation on intragenic recombination inDrosophila
Authors: Carlson Peter S. 
Published: September 2009

SUMMARYThe effects of heterozygous inversions and of theC(3)Gmutation on recombination between alleles of the rudimentary locus ofDrosophila melanogasterwere analysed. It is shown that the presence of either of these genetic alterations significantly changes the frequency and type of intragenic recombinants which are produced.
Histocompatibility mutations in mice: chemical induction and linkage with the H-2 locus
Authors: Egorov I. K. , Blandova Zinaida K. 
Published: September 2009

SUMMARYYoung mice of the strains A/Y and B10.D2 were repeatedly treated with diethylsulphate (DES) in different doses (36 to 1100 mg/kg). At the age of 9 weeks they were mated to females of the strains A. CA (‘A’ group) and C57BL/10Eg (‘D’ group) respectively. 2101 progeny of these matings were tested for histocompatibility by skin grafting. The spontaneous H-mutation rates were 6·96 × 10−4per gamete in the A group and 9·6 × 10−4per gamete in D group. In progeny of treated males the H-mutation rates were 0 in A group and 5·79 × 10−3per gamete in D group, showing apparent effect of paternal DES treatment on mutation frequency in the last group. Two mutations of theH-2locus were found, which together with the other threeH-2mutations published so far yielded a mutation rate of 5·18 × 10−4per gamete. The mutation rate of theH-2locus is higher than the expected rate per H-locus, indicating a great genetic complexity ofH-2.
Position of the translocation break T(2;9)138Ca in linkage group IX of the mouse
Authors: Klein Jan , Klein Dagmar 
Published: September 2009

SUMMARYThe translocation break T(2;9)138Ca is located about three map units from the H-2 region on the non-centromeric side of the IXth linkage group. The recombination frequency in the T-H-2 interval is increased in the presence of the T138 translocation to about twice its value in the absence of the translocation.
Sexuality in Neurospora crassa I. Mutations to male sterility
Authors: Weijer J. , Vigfusson N. V. 
Published: September 2009

SUMMARYMutations giving rise to sexual sterility were induced in Neurospora crassa macroconidia by ultraviolet-light irradiation. Thirty mutants were isolated on the basis of their male sterility in crosses with a wild-type strain. When used as the male parent these mutants exhibited a wide spectrum of sexual behaviour patterns ranging from the production of only small brown protoperithecia (complete male sterility) to the production of large and normally pigmented perithecia but with an undeveloped ostiole and very few if any spores. For many of the mutants the behaviour pattern is different when the strain is used as the female parent. Segregation data reveal that none of these mutants represent mutations of the mating-type locus. These findings suggest that the sexual development cycle is blocked at various stages in the different mutant strains. All attempts to restore fertility by supplying various additives to the medium or by varying the incubation time and temperature were unsuccessful. Conidial viability tests carried out on many of the strains revealed no abnormality in this respect. The aberrant segregation patterns exhibited by many of the mutants are discussed.
Evidence of non-random X chromosome activity in the mouse
Authors: Cattanach B. M. , Williams C. E. 
Published: September 2009

SUMMARYX-linked modification of the heterozygous phenotypes of X-linked genes has been detected in the X chromosomes of several inbred strains of mice. The effect is similar to that of the alternative ‘states’ or alleles, of theX chromosome controlling element, Xce, identified in T(1; X)Ct X chromosomes. Tests on two such differing X chromosomes have indicated that the phenotypic modification results either from non-random inactivation of the two X chromosomes or from selection operating on the two cell populations differentiated by X-inactivation. The data provide evidence of non-random X chromosome activity in the somatic cells of the female mouse.
Cortical morphogenesis inParamecium aurelia:mutants affecting cell shape
Authors: Whittle J. R. S. , Chen-Shan L. 
Published: September 2009

SUMMARYIn order to investigate the importance of the nuclear genotype during morphogenesis of the cortex inParamecium aurelia, a search was made for conditional and unconditional mutants affecting cell shape. Ten different mutants were readily recovered following mutagenesis withN-methyl-N-nitro-N-nitrosoguanidine on stock 51s of syngen 4. The detailed pattern of surface units remained unchanged in these mutants but each one can be described as resembling a normal cell twisted about its long axis. Nine of the mutants complement each other and show no linkage. The remaining mutant, a ‘chain former’, has conditional expression, and is only recognizable at 35 °C. The penetrance of this mutant is affected by the food organism used. The conditional mutant also interacts with seven of the other mutants in pairwise homozygous combinations so that in these genotypes it can be classified after growth at 25 °C. The mutants are discussed in relation to the search for genie effects on the cortical pattern.
Genetic locus determining resistance to phage BF23 and colicins E1, E2and E3inEscherichia coli
Authors: Jasper Paula , Whitney Eleanor , Silver Simon 
Published: September 2009

SUMMARYThe gene for resistance to phage BF23 and colicins E1, E2and E3,bfe, was mapped by a combination of conjugation and transduction crosses. Co-transduction ofbfewas found with markers in the region between 76 and 79 min on theEscherichia coligenetic map. The highest frequency of co-transduction was found withargH(47%). Three-factor transductional crosses showed unambiguously thatbfelies betweenargHandsupM, at about 77·5 min on the map.
Consequences of double cross-over detections on the functional interpretation of segment ‘29’ in Podospora anserina
Authors: Touré B. , Picard M. 
Published: September 2009

SUMMARYDouble cross-overs were detected in a few crosses involving segment ‘29’ mutants of locus ‘14’ in Podospora anserina. The occurrence of such recombination events made it necessary to reconsider the localization of three mutants. Use of an outside marker and the analysis of many other crosses allowed these mutants to be mapped unambiguously. The change in the localization of one of these mutants together with complementation tests on a new mutant leads to the conclusion that the polycistronic unit of transcription contains only four cistrons instead of the five previously thought to exist.
The genetics of some second chromosome melanotic tumour mutants ofDrosophila melanogaster
Authors: Sparrow John C. 
Published: September 2009

SummaryThe genetic relationships of the available second chromosome melanotic tumour mutants inDrosophila melanogasterhave been investigated. Complementation tests demonstrate the existence of new alleles of thetu bwlocus and show thattu-Wandtu-gare alleles. The data suggest that there is a minimum of three major gene loci on the second chromosome involved in tumorigenesis. A number of modifier genes were found which affect the penetrance of the major tumour genes analysed. These and the problems they cause in mapping the low penetrant tumour genes are discussed. It has not been possible to maptu-48a, tu- Wandtu-gaccurately, due largely to the presence of modifier genes. It appears that the genetic basis for melanotic tumour formation is complex.
The mutagenicity of amino acid analogues inCoprinus lagopus
Authors: Talmud Philippa J. , Lewis D. 
Published: September 2009

SummaryThe amino acid analoguesp-fluorophenylalanine (PFP) and ethionine (ETH) are strongly mutagenic inCoprinus lagopus. The most pronounced effect was found with suppressor mutations of themet-1locus. PFP, at a concentration of 2·4 × 10−4M, increased the mutation frequency 500 fold and ETH, at a concentration of 2·4 × 10−3M, 30 fold over the spontaneous mutation frequency. From the spectrum of suppressors of themet-1locus and the dominant revertants of thead-82locus, induced by analogue treatments, it was concluded that both analogues induce single base-change mutations. The dose response curves follow a sigmoid plot, revealing that within a certain range of analogue concentrations, muta-genesis is strongly dose dependent.Using analogue resistant mutants, it has been shown that PFP mutagenesis is a function of its incorporation into protein. However, ETH mutagenesis is independent of protein incorporation but can be correlated with the degree of ethylation of nucleic acids. The synergistic effect PFP and ETH supports the evidence of the different mutagenic actions of the two analogues.
The age of an allele in a finite population
Authors: Maruyama Takeo 
Published: September 2009

SUMMARYThe age of an allele segregating in a finite population may be defined in two ways. They are (1) the age of a mutant gene that has never reached fixation in the population, and (2) the age including any fixation period in the past. Theoretical expressions for these are derived on the assumption that every mutant is unique.
An extensive behavioural and genetic analysis of the Pawn mutants inParamecium aurelia
Authors: Chang Sheng-Yung , Houten Judith Van , Robles Laura J. , Lui Simmy S. , Kung Ching 
Published: September 2009

SUMMARYPawns are behavioural mutants which show impairment in membrane excitability and are, therefore, devoid of normal avoiding reactions. We obtained 103 lines of Pawns through mutagenesis and screening. Among those that yielded to breeding studies, 59 lines belonged to thepwAcomplementation group and 38 lines belonged to thepwBgroup. No other genic loci were found in this extensive analysis. Mutants of thepwAlocus showed various degrees of phenotypic leakiness. Based on the pheno- and genotypic differences, we estimated that at least 45 independent mutational events were represented in these 103 Pawn lines.
Chiasma variation and control in pollen mother cells and embryo-sac mother cells of rye
Authors: Davies E. D. G. , Jones G. H. 
Published: September 2009

SUMMARYMean chiasma frequencies and the amounts of between-bivalent chiasma variation were computed for pollen mother cells (p.m.c.) and embryo-sac mother cells (e.m.c.) of five distinct inbred rye lines. Despite the considerable differences for both these metrics shown by the different lines, very little variation was seen between p.m.c. and e.m.c. belonging to the same lines. It is concluded that chiasma formation in p.m.c. and e.m.c. of rye is governed and regulated by a single controlling system of genes and that variation in this genetic system is expressed identically in the two sexes.
Genetic analysis of amidase mutants ofPseudomonas aeruginosa
Authors: Betz Joan L. , Brown Jane E. , Clarke Patricia H. , Day Martin 
Published: September 2009

SUMMARYMutants ofPseudomonas aeruginosa, which differed in amide growth phenotype from the wild-type strain, were subjected to genetic analysis using the generalized transducing phage F116. The map order of some mutational sites was determined by 3-factor crosses in which a mutation in the linked regulator geneamiRwas used as the outside marker to determine the relative order of mutations in the amidase structural geneamiE. Acetamide-positive transductants were recovered in crosses between amidase-negative strains and strains PhB3(PAC377), V2(PAC353) and V5(PAC356) producing mutant amidases which hydrolyse phenylacetamide and valeramide but not acetamide. Some recombinants carried the mutationamiE16 determining the properties of the mutant B amidase produced by strain B6(PAC351) from which both PhB and V class mutants were derived, while other recombinants produced A amidase determined by the wild-typeamiEgene.
The role of latent viruses in subline differentiation in inbred strains of mice
Authors: Wickramaratne G. A. De S. 
Published: September 2009

SUMMARYThe possibility that changes in latent viruses would contribute to the differentiation of sublines in inbred strains of mice was investigated using the Bittner virus and the BALB/c strain of mice. The results show that, at least for this combination, there is no reason for implicating latent viruses in subline differentiation.
Genetic regulation and pattern formation: A study of theyellowlocus inDrosophila melanogaster
Authors: Nash William G. , Yarkin Rhoda J. 
Published: September 2009

SUMMARYMany of theyellowalleles found inDrosophila melanogasterresult in a unique pattern of phenotypic expression. These patterns follow the morphologically distinct cell types of the cuticle, so that for one allele all the bristles of the head and thorax might be mutant, while most of the fly appears wild type. A comparison of many differentymutants demonstrates that theyellowphenotype is expressed independently in most if not all the different cell types which form the cuticle. Control of this expression appears to reside at theyellowlocus itself.
Regulation of enzyme activities inDrosophila: I. The detection of regulatory loci by gene dosage responses
Authors: Rawls John M. , Lucchesi John C. 
Published: September 2009

SUMMARYIn order to detect regulatory genetic sites in the autosomes ofDrosophila melanogaster, the levels of X-linked glucose-6-phosphate dehydro-genase and autosomally linked α-glycerophosphate and isocitrate dehydrogenases have been monitored in extracts of flies aneuploid for regions of chromosomes II and III. In addition to expected structural gene dosage responses of α-GPDH and IDH, flies hyperploid for several autosome regions were found to display altered levels of one or more of the enzymes studied. While IDH activity was increased in flies hyperploid for segments of both chromosomes II and III, α-GPDH activity was decreased in specific hyperploids for chromosome II regions only. The latter group of segmental aneuploids were normal with respect to levels of chromosome II-linked alcohol dehydrogenase. To test if the observed responses were due to dosage changes of discrete genes lying within the larger effective segments, flies aneuploid for subdivisions of the chromosome segments 21A-25CD, 35A–40, and 70CD–71B were assayed. For two of these large segments so analysed, the apparent effects were attributable to specific small subdivisions, suggesting the presence of discrete regulatory sites within the latter. For the 35A–40 region the α-GPDH effect observed for subdivisions was not sufficient to account for the large α-GPDH decrease seen in flies hyperploid for the large, inclusive region. These observations are discussed with respect to the possible bases of effect of regulatory elements on enzyme activity.
Regulation of enzyme activities inDrosophila: II. Characterization of enzyme responses in aneuploid flies
Authors: Rawls John M. , Lucchesi John C. 
Published: September 2009

SUMMARYTo test whether large changes in the enzyme levels of segmentally aneuploidDrosophila melanogastercan be ascribed to changes in kinetic properties of the enzymes affected, comparisons have been made with regard to the heat stability, substrate concentration dependency, and the presence of heat-stable inhibitors or activators within the extracts of aneuploid and control flies. By these criteria, no differences were found between controls and the α-GPDH activity of flies trisomic for chromosome II segments 27D–31E, 35A–40, 41–45F, and 57B–60F and no differences were evident between the IDH properties of 70CD–71B aneuploids and their controls. The enzyme changes observed in these aneuploids are more likely associated with changes in the rates of accumulation of the enzyme molecules. The IDH of flies trisomic for the 27D–31E region was more heat-stable than that of controls while the α-GPDH of flies trisomic for the 21A–25CD region displayed an apparent Michaelis constant for α-glycerophosphate lower than that of controls. The possible bases for these latter qualitative distinctions are discussed.
Mitotic crossing-over in a higher plant
Authors: Carlson Peter S. 
Published: September 2009

SUMMARYThis paper provides direct evidence for the occurrence of mitotic crossing-over in leaf tissues andin vitrocell cultures ofNicotiana tabacum. The geno-typic composition of both segregating regions of twin spots was analysed byin vitroculture of the segregating tissue and by regenerating plants from this tissue. The frequency of mitotic crossing-over is influenced by several physical and chemical agents.
A note on increasing the limit of selection through selection within families
Authors: Dempfle Leo 
Published: September 2009

SUMMARYIt is shown that, in a finite population, by ensuring an equal contribution of offspring from each family we achieve a higher selection limit than by using mass selection, given that the correlation between selection criterion and additive genetic value is sufficiently high. The difference between the selection limits of the two schemes increases with more intense selection. The theoretical results were verified by Monte Carlo Simulation, and the influences of several factors were investigated. It is shown that such a breeding scheme might be useful in dairy cattle.