bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of effective population size from data on linkage disequilibrium
Authors: Hill William G. 
Published: September 2009

SUMMARYA method is proposed for estimating effective population size (N) from data on linkage disequilibrium among neutral genes at several polymorphic loci or restriction sites. The efficiency of the method increases with larger sample size and more tightly linked genes; but for very tightly linked genes estimates ofNare more dependent on long-term than on recent population history. Two sets of data are analysed as examples.
Mitochondrial mutagenesis inSaccharomyces cerevisiae: the origin ofmit−mutants
Authors: Putrament Aleksandra , Ejchart Anna 
Published: September 2009

SUMMARYYeast cells contain many copies of mitochondrial (mit) genomes. The question we tried to answer was howmit−mutations occurring in one genome as a result of mutagenic treatment might yield homoplasmic mutant cells. Three processes were considered. First, that these cells originate by segregation of mutant and standard alleles during cell division. Secondly, that they originate through intracellular selection, for which cell division is not required. Thirdly, that recombination involving the mutant and standard alleles is non-reciprocal and unidirectionalmit+→mit−so that the mutant allele is spread into the entire population of mitochondrial genomes within a cell, thus making it homoplasmicmit−. The results indicate that the first process, although efficiently producing homoplasmic cells from heteroplasmic zygotes (for review see Birky, 1978), seems to play only a minor, if any, role in producing homoplasmic mutant progenies from mutagenized cells. The most important is the second process, that is, intracellular selection occurring in cells which have one or a few genomes carryingmit−mutations, while the remaining genomes are irreversibly damaged. The third process, unidirectionalmit+→mit−conversion, does not seem to play any part.
The susceptibility to cortisone-induced cleft palate of recombinant inbred strains of mice: lack of association with theH-2haplotype
Authors: Vekemans M. , Taylor B. A. , Fraser F. C. 
Published: September 2009

SUMMARYRecombinant-inbred (RI) strains of mice derived from the cross of strains C57BL/6J and DBA/2J were used to study the inheritance of susceptibility to cortisone-induced cleft palate. Most of the RI strains could be classified as either resistant, like C57BL/6J, or susceptible, like DBA/2J, suggesting the segregation of a major locus. An association with the phosphoglucomutase-1 locus (Pgm-1) on Chromosome 5 was observed. There was no association with the H-2 locus on Chromosome 17 as had been reported in previous studies utilizing different strains. We conclude that susceptibility to cortisone-induced cleft palate may be determined by different loci depending on the strains studied.
Copper localization in the duodenal mucosa of heterozygous tortoiseshell (Moto/+) female mice (Mus musculus)
Authors: Sheedlo Harold J. , Beck Melvin L. 
Published: September 2009

SUMMARYThe duodenal mucosa of normal (+/+) and heterozygous tortoiseshell (Moto / +) female mice was analysed by an ultrastructural histochemical copper localization technique. Copper was rarely detected along the duodenal microvilli of + / + female mice. However, copper was localized on the surface of the brush border of the duodenal mucosa and within pinocytotic vesicles at the base of the microvilli of Moto /+ female mice. The mottled defect may involve a defective intestinal uptake of copper, as well as a faulty copper transport mechanism.
Nucleotide sequences of highly repeated DNAs; compilation and comments
Authors: Miklos George L. Gabor , Gill Amanda Clare 
Published: September 2009

SummaryThe nucleotide sequence data from highly repeated DNAs of inverte-brates and mammals are summarized and briefly discussed. Very similar conclusions can be drawn from the two data bases. Sequence complexities can vary from 2 bp to at least 359 bp in invertebrates and from 3 bp to at least 2350 bp in mammals. The larger sequences may or may not exhibit a substructure. Significant sequence variation occurs for any given repeated array within a species, but the sources of this heterogeneity have not been systematically partitioned. The types of alterations in a basic repeating unit can involve base changes as well as deletions or additions which can vary from 1 bp to at least 98 bp in length. These changes indicate that sequenceper seis unlikely to be under significant biological constraints and may sensibly be examined by analogy to Kimura's neutral theory for allelic variation. It is not possible with the present evidence to discriminate between the roles ofneutralandselectivemechanisms in the evolution of highly repeated DNA.Tandemly repeated arrays are constantly subjected to cycles of amplification and deletion by mechanisms for which the available data stem largely from ribosomal genes. It is a matter of conjecture whether the solutions to the mechanistic puzzles involved in amplification or rapid redeployment of satellite sequences throughout a genome will necessarily give any insight into biological functions.The lack of significant somatic effects when the satellite DNA content of a genome is significantly perturbed indicates that the hunt for specific functions at thecellularlevel is unlikely to prove profitable.The presence or in some cases theamountof satellite DNA on a chromosome, however, can have significant effects in the germ line. There the data show that localized condensed chromatin, rich in satellite DNA, can have the effect of rendering adjacent euchromatic regionsrec−, or of altering levels of recombination on different chromosomes. No data stemming from natural populations however are yet available to tell us if these effects are of adaptive or evolutionary significance.
Aberrant segregation patterns and gene mappability inAscobolus immersus
Authors: Leblon G. , Haedens V. , Kalogeropoulos A. , Paquette N. , Rossignol J.-L. 
Published: September 2009

SummaryCrosses between various types of mutant giving specific patterns of aberrant segregation were performed in theb2spore colour locus ofAscobolus immersus. The map of 41 mutations showing various patterns of aberrant segregation was established. The frequency of wild-type recombinants and the map additivity, map expansion and map contraction characteristics were shown to be strongly dependent upon the pattern of aberrant segregation of the mutations used. Mutations giving no postmeiotic segregation and an excess of conversion to wild type over conversion to mutant exhibit map expansion in small intervals and a strong map contraction in large intervals. Mutations giving postmeiotic segregations also exhibit map contraction in large intervals. Mutations giving no postmeiotic segregations and an excess of conversion to mutant over conversion to wild type show map additivity and thus provide a simple way for devising gene maps. The relationship between the mapping properties and the pattern of aberrant segregations is accounted for when considering parameters of gene conversion: frequency and distribution of hybrid DNA, frequency and direction of mismatch correction.
The cytogenetic boundaries of the rDNA region within heterochromatin of theXchromosome ofDrosophila melanogasterand their relation to male meiotic pairing sites
Authors: Appels R. , Hilliker A. J. 
Published: September 2009

SummaryThe proximal breakpoints of the inversion chromosomesIn(1)ωm4andIn(1)m51bwere shown, byin situhybridization, to define the boundaries of the ribosomal DNA region located within theXchromosome heterochromatin (Xh). We estimate thatat least95% of the rDNA is located between theIn(1)ωm4andIn(1)ωm51bproximal breakpoints. In contrast only 60–70% of the Type I intervening sequences located inXhare located between these breakpoints. The Type I intervening sequences in the rDNA region occur as inserts in the 28S rRNA sequences while the remainder of the sequences are distal to theIn(1)ωm4breakpoint and not associated with rRNA genes.The regions of Xh which contain rDNA and Type I intervening sequences were related to regions shown by Cooper (1964) to contribute to meiotic pairing between theXandYchromosomes in male Drosophila. We demonstrate that the rRNA coding region contributes toX/Ypairing. However, no single region of Xh is required for fidelity of male meiotic pairing of the sex chromosomes.
Path analysis under generalized assortative mating: II. American I.Q.
Authors: Rao D. C. , Morton N. E. , Lalouel J. M. , Lew R. 
Published: September 2009

SummaryRice, Cloninger & Reich (1980) showed that correlational data on American I.Q. is consistent with a rather low genetic heritability. Here we confirm their general results with a more parsimonious model. From phenotypic data alone, the estimates of genetic and cultural heritability are 0·31 and 0·42, respectively. Using environmental indices, the parsimonious estimates become 0·34 and 0·26, respectively.
Non-selfing mutants from selfing (Het−) strains ofPhysarum polycephalum
Authors: Honey N. K. , Poulter R. T. M. , Aston R. J. 
Published: September 2009

SummaryPlasmodial formation in the MyxomycetePhysarum polycephalumis under heterothallic control by a mating type (mt) locus. In natural isolates only amoebae with differentmtalleles are able to cross to form diploid plasmodia. A class of mutants isolated from heterothallic amoebae, together with the variant strainCL, is able to form plasmodia in pure clones, designated as selfing. Non-selfing mutants have been isolated fromCLand from other selfing amoebae.This paper reports the isolation and analysis of 64 non-selfing derivatives (designated Npf−) from seven selfing (Het−) strains. The Npf−mutants could be grouped into eight classes on the basis of their crossing and complementation patterns. The possible significance of these mutants is discussed.
Genetic differentiation of quantitative characters between populations or species: I. Mutation and random genetic drift
Authors: Chakraborty Ranajit , Nei Masatoshi 
Published: September 2009

SummaryIntroducing a new genetic model called the discrete allelic-state model, the evolutionary change of genetic variation of quantitative characters within and between populations is studied under the assumption of no selection. This model allows us to study the effects of mutation and random genetic drift in detail. It is shown that when the allelic effects on phenotype are additive, the rate of approach of the genetic variance within populations to the equilibrium value depends only on the effective population size. It is also shown that the distribution of genotypic value often deviates from normality particularly when the effective population size and the number of loci concerned are small. On the other hand, the interpopulational variance increases linearly with time, if the intrapopu-lational variance remains constant. Therefore, the ratio of interpopulational variance to intrapopulational variance can be used for testing the hypothesis of neutral evolution of quantitative characters.
A new allele sash (Wsh) at theW-locus and a spontaneous recessive lethal in mice
Authors: Lyon Mary F. , Glenister P. H. 
Published: September 2009

SummaryA mutation to an apparently new allele at theW-locus of the mouse arose spontaneously in a cross between two inbred strains. Heterozygotes have a broad white sash, leading to the name and symbol sash,Wsh. Homozygotes are black-eyed whites which are viable, fertile and not anaemic, although the gene does cause mild haematopoietic defects. The original mutant animal also carried a spontaneous recessive lethal mutation on chromosome 5, mapping at 2 cM distal to theW-locus.
Genetic fine-structure of theGA-1locus in the higher plantArabidopsis thaliana(L.) Heynh
Authors: Koornneef M. , Van Eden J. , Hanhart C. J. , De Jongh A. M. M. 
Published: September 2009

SUMMARYNon-germinating gibberellin (GA) responsive mutants are a powerful tool to study genetic fine structure in higher plants. Nine alleles (EMS-and fast neutron-induced) of thega-1locus ofArabidopsis thalianawere tested in a complete half-diallel. No wild type ‘recombinants’ were found in the selfed progeny of 9 homoallelic combinations (in total 3 × 105plants); in the progenies from the 36 selfed hetero allelics the wild type frequency ranged from zero to 6·6 × 10−4. These frequencies allowed the construction of an internally consistent map for five different sites representing eight alleles. The ninth allele covered three sites and thus behaved like an intragenic deletion. The estimate of the total genetic length of thega-1locus was 0·07 cM. The order of the sites was also clearly reflected by the association with proximal outside markers. On the assumption that wild type gametes predominantly arise from reciprocal events, it was shown that a cross-over within thega-1locus leads to positive interference in the adjacent region.The results are discussed with respect to the mutagen used, the frequencies found in other plant and Drosophila genes, and the possible occurrence of gene conversion.
X-chromosome segregation, maternal age and aneuploidy in the XO mouse
Authors: Brook J. D. 
Published: September 2009

SUMMARYCytogenetic studies have ascertained that the segregation of the X-chromosome, during the first meiotic division of the oocyte in XO mice, occurs at random, contrary to the finding of some earlier authors. The ratio of nullo-X to X-bearing oocytes at ovulation does not change with maternal age. The usefulness of the XO mouse as a model for aneuploidy production in women (Lyon & Hawker, 1973) is discussed.
Transposon-Directed Mutagenesis and Chromosome Mobilization in Acinetobacter calcoaceticus EBF65/65
Authors: Towner K. J. 
Published: September 2009

SUMMARYRP4::Mu was used to insert Tn3171 into the Acinetobacter calcoaceticus EBF65/65 chromosome. Insertions occurred at a frequency of approximately 10−7 per recipient cell. Auxotrophic mutations resulted from 28% of the Tn3171 insertions examined, with a possible ‘hot-spot’ for insertion in a gene for arginine biosynthesis. The frequency of subsequent precise excision of Tn3171 from the chromosome was less than 10−10. When attempts were made using RP4 derivatives to mobilize the chromosome from a strain containing an arg::Tn3171 insertion, it was found that the enhanced transfer frequency of the adjacent region of the chromosome was dependent on the original Tn3171 insertion, but was independent of the presence of Tn3171 on the mobilizing plasmid.
Genetic variation of wild mouse populations in southern Germany: II. Serological study
Authors: Figueroa Felipe , Zaleska-Rutczynska Zofia , Adolph Sabine , Nadeau Joseph H. , Klein Jan 
Published: September 2009

SUMMARYA total of 207 wild mice trapped at different localities in southern Germany were tested for the presence of antigenic determinants controlled by class I genes (KandD) of theH-2complex. The test was based on the complement-dependent killing of lymphocytes in the micro-cytotoxicity assay. Both private (allele-specific) and public (shared) determinants were tested using polyclonal and monoclonal antibodies. The results of the H-2 typing were in agreement with karyological typing which divided the sampled mice into 5 populations. Each population was characterized by a certain antigenic profile (occurrence of individual determinants at certain frequencies); the profiles of the individual populations were sufficiently unique to differentiate these populations but at the same time sufficiently similar to indicate common origin of the populations. The karyological typing of the same mice reveals that all 5 populations share 1 pair of metacentric chromosomes,Rb(4.12)1Tu, but that, in addition, each population has at least one metacentric chromosome differentiating it from other populations. We interpret these findings as evidence that all wild mice in southern Germany stem from a common stock in which theRb(4.12)1Tutranslocation became fixed and which subsequently differentiated into the individual populations. This differentiation is accompanied by the fixation of new Robertsonian translocations (different ones in different populations) and the acquisition of characteristic H-2 antigenic profiles.
An investigation into the origins of meiotic aneuploidy using ascus analysis
Authors: Fulton A. M. , Bond D. J. 
Published: September 2009

SUMMARYAneuploidy can result from a variety of defects at meiosis. Results are presented of crosses ofSordaria brevicollisin which aneuploid spores are detected through complementation of spore colour mutants at thebufforgrey-6 loci on linkage groups II and IV respectively. By using ascus analysis, the underlying cause of the aneuploidy can be deduced in many cases. Thus non-conjuction (pairing failure) and non-disjunction at the first meiotic division, premature centromere division, non-disjunction at the second division, and pre-meiotic errors such as extra replication of the chromosomes can be distinguished. Both linkage groups were found to give a similar proportion of the different errors. Non-conjunction and first-division non-disjunction formed 60–70% of detectable cases, whilst premature centromere division and second-division non-disjunction comprised 10% and 5% of aneuploids respectively. However, only a small proportion of second-division errors are detected.It is proposed that the systems described in this paper can form the basis of a valuable screening method for detecting agents which increase aneuploid frequency. The advantages and disadvantages of using lower eukaryotes in this way are discussed.
Chromosomal locations of elevenElytrigia elongata(=Agropyron elongatum) isozyme structural genes
Authors: Hart Gary E. , Tuleen Neal A. 
Published: September 2009

SUMMARYThe zymogram phenotypes of 11 enzymes were determined for 22Triticum aestivumcv. Chinese Spring-Elytrigia elongatadisomic and ditelosomic chromosome addition lines. Eleven isozyme structural genes were located in specific arms of sixE. elongatachromosomes, as follows:Gpi-E1in 1ES,Est-E1in 3ES,Got-E3in 3EL,Adh-E1andLpx-E1in 4ES,Adh-E2andLpx-E2in 5EL,Amp-E1in 6Eα,Adh-E3andGot-E2in 6Eβ, andEp-E1in 7EL. TheE. elongatachromosomes present in five disomic addition lines have previously been designated 1E, 2E, 4E, 6E, and 7E to indicate their homoeology with Chinese Spring chromosomes. The results of this study support these designations. The development of disomic putative 3E and 5E addition lines is reported. The added chromosomes designated IV, V, and VI that are present in three of the seven original disomicT. aestivum-E. elongataaddition lines are translocated. Evidence that VL and VIL are opposite arms of 2E and that IV is partially homoeologous to 3E has been published. The results reported in this paper indicate that IVS = 3ES, IVL = 7EL, VS = 3ES, and VIS = 5ES and are consistent with VL and VIL being opposite arms of 2E. The synteny relationships of the 11E. elongataisozyme genes identified in this study are fully consistent with those of homoeologousT. aestivumcv. Chinese Spring genes and thus provide evidence that the gene synteny groups which these two species inherited from their common ancestor are conserved. This study further documents the valuable role that studies of isozyme genes can play in the isolation, characterization, and maintenance of alien chromosomes, telosomes, and chromosomal segments in wheat strains.
Macrogeographic genetic variation in a human commensal:Aedes aegypti, the yellow fever mosquito
Authors: Wallis Graham P. , Tabachnick Walter J. , Powell Jeffrey R. 
Published: September 2009

SUMMARYGenetic variation at 11 enzyme loci inAedes aegyptipopulations collected from 63 localities around the world is presented. A UPGMA tree based on genetic distance values clusters populations of sylvanA. aegypti formosusfrom West Africa and East Africa together, along with Asian and south-eastern U.S. populations. DomesticA. aegypti aegyptifrom East Africa and all other New World populations form the other major cluster. Multivariate discriminant analysis allows recognition of seven major global ‘genetic–geographic’ groups, which are consistent with the genetic distance data. Populations from the south-eastern U.S. are clearly genetically distinct from other U.S. and Mexican populations. This distinct gene pool may be indicative of reinfestation of areas whereA. aegyptiappears to have been absent in the recent past. Other evolutionary and epidemiological implications of the genetic population structure ofAedes aegyptiare discussed.
Biochemical genetics of Neurospora nuclease II: Mutagen sensitivity and other characteristics of the nuclease mutants
Authors: Mishra N. C. , Forsthoefel A. M. 
Published: September 2009

SUMMARYFive newnucmutants ofNeurospora crassawere characterized for their relative sensitivities to different mutagens (UV, MNG, MMS), to mitomycin-C and to histidine; latter has been shown to inhibit the growth of certain UV sensitive mutants. These mutants were also compared for their capabilities for spontaneous mutation as determined by resistance to p-fluoro-phenylalanine. Based on these characterization, the mutants seem to belong to two groups. The first group includednuc-3andnuc-6which showed sensitivity to all mutagen tested and possessed capability for a very high frequency of spontaneous mutation (i.e. mutator effect). The second group includednuc-4, nuc-5andnuc-7; these were as resistant to different mutagens as the wild type strain, but possessed an antimutator effect (i.e. the frequency of spontaneous mutation by these three mutants were at least 0·5–100 × less than the wild type strains). There was some variation in these properties of mutants belonging to the two groups. Among all the fivenucmutants,nuc-3was characterized by extreme sensitivity to all mutagens. None of the fivenucmutants were sensitive to histidine. The properties ofnucmutants are discussed in relation to their possible role in DNA repair and recombination.
The population dynamics of transposable elements
Authors: Charlesworth Brian , Charlesworth Deborah 
Published: September 2009

SUMMARYThis paper describes analytical and simulation models of the population dynamics of transposable elements in randomly mating populations. The models assume a finite number of chromosomal sites that are occupable by members of a given family of elements. Element frequencies can change as a result of replicative transposition, loss of elements from occupied sites, selection on copy number per individual, and genetic drift. It is shown that, in an infinite population, an equilibrium can be set up such that not all sites in all individuals are occupied, allowing variation between individuals in both copy number and identity of occupied sites, as has been observed for several element families inDrosophila melanogaster. Such an equilibrium requires either regulation of transposition rate in response to copy number per genome, a sufficiently strongly downwardly curved dependence of individual fitness on copy number, or both. The probability distributions of element frequencies, generated by the effects of finite population size, are derived on the assumption of independence between different loci, and compared with simulation results. Despite some discrepancies due to violation of the independence assumption, the general pattern seen in the simulations agrees quite well with theory.Data fromDrosophilapopulation studies are compared with the theoretical models, and methods of estimating the relevant parameters are discussed.