bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fixation probability in spatially changing environments
Authors: Tachida Hidenori , Iizuka Masaru 
Published: September 2009

SummaryThe fixation probability of a mutant in a subdivided population with spatially varying environments is investigated using a finite island model. This probability is different from that in a panmictic population if selection is intermediate to strong and migration is weak. An approximation is used to compute the fixation probability when migration among subpopulations is very weak. By numerically solving the two-dimensional partial differential equation for the fixation probability in the two subpopulation case, the approximation was shown to give fairly accurate values. With this approximation, we show in the case of two subpopulations that the fixation probability in subdivided populations is greater than that in panmictic populations mostly. The increase is most pronounced when the mutant is selected for in one subpopulation and is selected against in the other subpopulation. Also it is shown that when there are two types of environments, further subdivision of subpopulations does not cause much change of the fixation probability in the no dominance case unless the product of the selection coefficient and the local population size is less than one. With dominance, the effect of subdivision becomes more complex.
Analysis of lines of mice selected on fat content: 4. Correlated responses in growth and reproduction
Authors: Hastings Ian M. , Yang Jianyi , Hill William G. 
Published: September 2009

SummaryLines of mice have been selected for 32 generations for either high or low fat content, resulting in a threefold divergence in the selection criterion (estimated fat content of males at 14 weeks of age). Male mice from both lines were dissected at a series of ages between 4 and 26 weeks and the following traits measured or estimated: body weight, fat content, lean weight, and the weights of several fatpads and internal organs. The lines appeared to have a similar underlying lean weight upon which the Fat line accumulated fat at a faster rate. This accumulation continued unabated in the Fat lines for at least 26 weeks but had effectively ceased by 8 weeks of age in the Lean. The liver and kidneys were slightly larger in the Fat line but there were no differences in the weights of heart, lung or spleen. This detailed phenotypic description of the lines complemented previous reports describing correlated changes in their physiology. The threefold divergence in estimated fat content was less than that in one of its component traits, growth of gonadal fatpad, but was greater than the divergence in other physiological indicators, i.e. the activity of lipogenic enzymes in vitro and direct measurement of lipogenic flux. Testis size in the Fat line was consistently lower than in the Lean although the Fat line was slightly more fecund, apparently due to a higher prenatal survival rate.
Accumulation of P elements in minority inversions in natural populations ofDrosophila melanogaster
Authors: Eanes Walter F. , Wesley Cedric , Charlesworth Brian 
Published: September 2009

SummaryThe accumulation of a transposable element inside chromosomal inversions is examined theoretically by a mathematical model, and empirically by counts of P elements associated with inversion polymorphisms in natural populations ofDrosophila melanogaster. The model demonstrates that, if heterozygosity for an inversion effectively reduces element associated production of detrimental chromosome rearrangements, a differential accumulation of elements is expected, with increased copy number inside the minority inversion. Several-fold differential accumulations are possible with certain parameter values. We present data on P element counts for inversion polymorphisms on all five chromosome arms of 157 haploid genomes from two African populations. Our observations show significantly increased numbers of elements within the regions associated with the least common, or minority arrangements, in natural inversion polymorphisms.
Deletion of mouset-complex distorter-1 produces an effect like that of thet-form of the distorter
Authors: Lyon Mary F. 
Published: September 2009

SummaryAn allele of the mouse brachyury locus,T22H, had been shown previously to involve a deletion of several markers in the proximal part of chromosome 17, and almost certainly includes deletion of thet-complex distorter geneTcd-1. The effects ofT22Hon transmission ratio distortion and male sterility caused by thet-complex were compared with those of a partialt-haplotypeth51, which carries the t-form of the distorterTcd-1t. In combination with the complete haplotypetf32,T22Hcaused severe impairment of male fertility, but males of genotypeT22H/t6orT22H/thSlwere normally fertile. These results were very similar to those obtained whenth51was in combination with the same haplotypes. In effect on transmission ratioT22Hwas again similar tothSI, in that it produced a marked increase in the transmission of the haplotypet6. To test whether the effects ofT22Hwere due to deletion of elements other thanTcd-1, the effect ofT22Hon transmission of the partial haplotypeth2was compared with that of the deletionThv. AgainT22Hmarkedly increased transmission of the t-haplotype and the effect was significantly greater than the small effect produced byThp.It is concluded that deletion of the distorterTcd-1has an effect like that of thet-form of this distorter,Tcd-1t, and hence that Ted-11 must be an amorph or hypomorph. It is speculated that othert-complex distorters,Tcd-2tandTcd-3tmay also be amorphs or hypomorphs. Thus, the phenomena of transmission ratio distortion and male sterility due to thet-complex appear to be brought about by differential susceptibility of wild-type andt-responder alleles,Tcr+andTcrt, to a shortage of distorter gene product.
Induction of mutations in the zebrafish with ultraviolet light
Authors: Grunwald David Jonah , Streisinger George 
Published: September 2009

SummaryRecessive lethal germline and specific locus somatic mutations were induced efficiently in the zebrafish by exposure of mature sperm to UV light. Mutagenesis of sperm yielded mosaic individuals: clones bearing novel mutations represented approximately 12–25% of the haploid germ cells and 25–50 % of the somatic tissue. Simple methods are described for the reliable identification and propagation of newly arising developmental mutations in zebrafish.
Induction of recessive lethal and specific locus mutations in the zebrafish with ethyl nitrosourea
Authors: Grunwald David Jonah , Streisinger George 
Published: September 2009

SummaryRecessive lethal mutations and mutations at thegol-1locus were induced in the zebrafish by exposure of mature sperm to the alkylating agent ethyl nitrosourea (ENU). Embryonic lethal phenotypes were recognized among the parthenogenetic progeny of mutagenized animals or among the progeny of daughters of mutagenized animals. Novel specific locus mutations were identified by the failure of mutagenized chromosomes to complement pre-existing mutant alleles at the gol-1 locus. Each mutagenized individual harboured approximately 10 embryonic lethal mutations in its germ line and about 1 in 500 mutagenized animals harboured a new mutation at thegol-1locus. Three lines of evidence indicate that the majority of mutations that were recovered following treatment of mature sperm with ENU were probably point mutations. First, the soma and germ lines of mutagenized animals were mosaic, as expected following simple alkylation of sperm DNA. Second, mutations induced by ENU at thegol-1locus affected pigmentation but not viability, unlike the majority of mutations induced at this locus with y-irradiation. Third, the ratio of specific locus: recessive lethal mutations induced by ENU was approximately 50-fold lower than the ratio observed following mutagenesis with y-rays. Comparison of the incidence with which embryonic recessive lethal mutations were induced with the incidence with which specific locus mutations arose indicates that there are greater than 5000 genes essential to the development and viability of the zebrafish embryo.
Two isoforms of the kidney androgen-regulated protein are encoded by two alleles of a single gene in OFl mice
Authors: Melanitou E. , Tronik D. , Rougeon F. 
Published: September 2009

SummaryTwo cDNA clones coding for two forms of the mouse kidney androgen-regulated protein (KAP) distinguished by their electrophoretic mobilities on SDS gel electrophoresis have been isolated from libraries prepared from strains of mice having one (BALB/c) or two (OFl) forms of the KAP protein. The corresponding mRNAs have identical sizes, as well as identical sequences in their 5' non-translated regions. The size difference observed between the two proteins is due to two point mutations in the coding region of the KAP mRNA, leading to two amino-acid changes one of which resulted in the substitution of a glycine for a glutamic acid. As shown byin vitrotranscription/translation experiments, these two amino-acid differences are responsible for the shift in the apparent molecular weight of the protein on SDS gels. Both forms of the protein are more abundant in males than in females.In vitrotranslation of kidney RNAs isolated from six different strains and species of mice revealed the presence of other forms of the KAP protein, characterized by small variations of their molecular weights. Southern blot analysis data are consistent with the presence of only onekapgene in the mouse genome. A restriction fragment length polymorphism has been observed, which does not correlate with the protein polymorphism, indicating the presence of another allele in the OF1 mouse genome.
The estimation of genotypic probabilities in an adult population by the analysis of descendants
Authors: Barbadilla Antonio , Naveira Horacio , Ruiz Alfredo , Santos Mauro 
Published: September 2009

SummaryThere are instances, the most typical being inversion polymorphism inDrosophila, where the genotype is not directly accessible in the adult organism, but can be observed in young life-stages. In these cases, if we want to estimate genotypic probabilities in adult populations, we must examine an offspring sample from adults. In this paper we derive the maximum likelihood estimators, and their errors, for genotypic probabilities in an adult population, according to a standard protocol in which collected parents of a random sample are individually crossed with individuals of a laboratory stock with known homozygous genotype, and a fixed number of their offspring is genetically examined in young life-stages. Arnold's probabilistic model for one locus with two alleles is developed for our estimates. An optimum design which generates a minimum variance is proposed, consisting of examining a moderate offspring number (3–4) per parent. Finally, we propose maximum likelihood estimates when several samples with different numbers of parents per sample, and/or examined progeny per parent are obtained.
Estimating effective population size from samples of sequences: inefficiency of pairwise and segregating sites as compared to phylogenetic estimates
Authors: Felsenstein Joseph 
Published: September 2009

SummaryIt is known that under neutral mutation at a known mutation rate a sample of nucleotide sequences, within which there is assumed to be no recombination, allows estimation of the effective size of an isolated population. This paper investigates the case of very long sequences, where each pair of sequences allows a precise estimate of the divergence time of those two gene copies. The average divergence time of all pairs of copies estimates twice the effective population number and an estimate can also be derived from the number of segregating sites. One can alternatively estimate the genealogy of the copies. This paper shows how a maximum likelihood estimate of the effective population number can be derived from such a genealogical tree. The pairwise and the segregating sites estimates are shown to be much less efficient than this maximum likelihood estimate, and this is verified by computer simulation. The result implies that there is much to gain by explicitly taking the tree structure of these genealogies into account.
Induced expression of a Drosophila hsp70 promoter-fusion transgene is reduced after repeated heat shocks
Authors: Hunt S. M. N. , Wilkins M. R. , Stokes H. W. , Daggard G. E. , Frankham R. 
Published: September 2009

SummaryLevels of transcripts produced by a heat shock protein 70 (hsp70)-antisense white transgene in Drosophila were measured after single and multiple heat shocks to determine whether the hsp70 promoter could produce sustained high levels of transgene transcripts. A single heat shock resulted in typical highly inducible levels of RNA, but the amount of antisense RNA was substantially reduced after multiple heat shocks. Endogenous hsp70 mRNA levels were also less abundant after multiple heat shocks as compared to a single heat shock. The hsp70 promoter is unsuitable for use in fusion gene constructs for long term expression studies where repeated heat shocks are required.
Population genetic aspects of deleterious cytoplasmic genomes and their effect on the evolution of sexual reproduction
Authors: Hastings Ian M. 
Published: September 2009

SummaryA conflict of interest may arise between intra-cellular genomes and their host cell. The example explicitly investigated is that of a ‘selfish’ mitochondrion which increases its own rate of replication at the cost of reduced metabolic activity which is deleterious to the host cell. The results apply to deleterious cytoplasmic agents in general, such as intracellular parasites. Numerical simulation suggests that selfish mitochondria are able to invade an isogamous sexual population and are capable of reducing its fitness to below “5 % of that prior to their invasion. Their spread is enhanced by decreasing the number of mitotic divisions between meioses, and this may constitute a significant constraint on the evolution of lifecycles. The presence of such deleterious cytoplasmic agents favours a nuclear mutation whose expression prevents cytoplasm from the other gamete entering the zygote at fertilization, resulting in uniparental inheritance of cytoplasm. Such a mutation appears physiologically plausible and can increase in frequency despite its deleterious effect in halving the amount of cytoplasm in the zygote. It is suggested that these were the conditions under which anisogamy evolved. These results have implications for the evolution of sexual reproduction. Standard theory suggests there is no immediate cost of sex, a twofold cost being incurred later as anisogamy evolves. The analysis described here predicts a large,rapidreduction in fitness associated with isogamous sexual reproduction, due to the spread of deleterious cytoplasmic agents with fitness only subsequently rising to amaximumtwofold cost as uniparental inheritance of cytoplasm and anisogamy evolve.
Fine structure mapping and complementation studies of themetDmethionine transport system inSalmonella typhimurium
Authors: Grundy Carolyn E. , Ayling P. D. 
Published: September 2009

SummaryA fine structure deletion map of themetDregion of the chromosome ofSalmonella typhimuriumresponsible for a high-affinity methionine transport system has been constructed. Complementation tests involving the introduction ofmetD+DNA contained in a pUC8 vector intometDstrains indicated the presence of four complementation groups in themetDregion. This suggested that the methionine system belongs to the osmotic shock-sensitive class of transport system, and therefore should possess a periplasmic methionine-binding protein and several membrane proteins. But a deletion mutation covering all knownmetDpoint mutations did not affect the level of a methionine binding activity in osmotic shock fluids, suggesting either that the deletion did not extend into the gene encoding the binding protein, or that the binding activity is not associated with themetDsystem. Possible reasons for the failure to isolate mutations in the gene for the binding protein are discussed.
Genetics of sexual isolation in females of theDrosophila simulansspecies complex
Authors: Coyne Jerry A. 
Published: September 2009

SummaryGenetic analysis of hybrids betweenDrosophila simulansandD. sechelliashows that sexual isolation in females is caused by at least two genes, one on each major autosome, while the X chromosome has no effect. These results are similar to those of a previous study of hybrids betweenD. simulansand another sibling species,D. mauritiana. In this latter hybridization, each arm of the second chromosome carries genes causing sexual isolation in females, implying a total divergence of at least three loci. The genetic similarity between theD. simulans/D.mauritianaandD. simulans/D.sechelliahybridizations probably results from independent evolution and not phylogenetic artifacts, because the dominance relationships and behavioural interactions differ between the two hybridizations. The lack of an X-chromosome effect on sexual isolation contrasts with genetic studies of post-zygotic reproductive isolation, which invariably show strong effects of this chromosome.
The distribution of transposable elements within and between chromosomes in a population ofDrosophila melanogaster. I. Element frequencies and distribution
Authors: Charlesworth Brian , Lapid Angela , Canada Darlene 
Published: September 2009

SummaryData were collected on the distribution of nine families of transposable elements among second and third chromosomes isolated from a natural population ofDrosophila melanogaster, by means ofin situhybridization of element probes to polytene chromosomes. It was found that the copy numbers per chromosome in the distal sections of the chromosome arms followed a Poisson distribution. Elements appeared to be distributed randomly along the distal sections of the chromosome arms. There was no evidence for linkage disequilibrium in the distal sections of the chromosomes, but some significant disequilibrium was detected in proximal regions. There were many significant correlations between different element families with respect to the identity of the sites that were occupied in the sample. There were also significant correlations between families with respect to sites at which elements achieved relatively high frequencies. Element frequencies per chromosome band were generally low in the distal sections, but were higher proximally. These results are discussed in the light of models of the population dynamics of transposable elements. It is concluded that they provide strong evidence for the operation of a force or forces opposing transpositional increase in copy number. The data suggest that the rate of transposition perelement per generation is of the order of 10−4, for the elements included in this study.
Recombination between the X and Y chromosomes and the Sxr region of the mouse
Authors: McLaren Anne , Simpson Elizabeth , Bishop Colin E. , Mitchell Michael J. , Darling Susan M. 
Published: September 2009

SummaryThe Sxr (sex-reversed) region that carries a copy of the mouse Y chromosomal testis-determining gene can be attached to the distal end of either the Y or the X chromosome. During male meiosis, Sxr recombined freely between the X and Y chromosomes, with an estimated recombination frequency not significantly different from 50% in either direction. During female meiosis, Sxr recombined freely between the X chromosome to which it was attached and an X-autosome translocation. A male mouse carrying the original Sxraregion on its Y chromosome, and the shorter Sxrbvariant on the X, also showed 50% recombination between the sex chromosomes. Evidence of unequal crossing-over between the two Sxr regions was obtained: using five markers deleted from Sxrb, 3 variant Sxr regions were detected in 159 progeny (1·9%). Four other variants (one from the original cross and three from later generations) were presumed to have been derived from illegitimate pairing and crossing-over between Sxrband the homologous region on the short arm of the Y chromosome. The generation of new variants throws light on the arrangement of gene loci and other markers within the short arm of the mouse Y chromosome.
A nuclear gene modifying instability of fertility restoration in cytoplasmic male sterile rice
Authors: Sano Yoshio , Eiguchi Mitsugu , Hirano Hiro-Yuki , Yamada Masa-Aki 
Published: September 2009

SummaryThe present study was carried out to examine the genetic mechanism responsible for reversions to fertile phenotype detected in cytoplasmic male-sterile plants of rice. Thecms-bocytoplasm of Chinsurah boro II gave rise to male-sterility in plants without a gametophytic restorer gene (Rf1). Taichung 65 (T65A) was known to be the maintainer which carries no restorer; however, Taichun 65 preserved in our laboratory (T65B) showed partial fertility (about 8% seed set) when crossed with the male-sterile plants. Unexpectedly, the seed fertility gradually increased with repeated selfings and almost fully fertile plants were obtained in the F6generation. The cytoplasmic substitution lines revealed that reversions to fertile phenotype resulted from mutational events at the nuclear level. The genetic experiments indicated that the partial fertility observed in the F1hybrid was controlled by a dominant gene,Ifr1, which was carried by T65B. The results obtained suggested thatIfr1itself was associated with instability of fertility restoration in the presence ofcms-bocytoplasm since partially fertile plants carryingIfr1always showed a tendency for gradual increase in fertility in the later generations. The results are also discussed in relation to a rapid genetic change through intensified gametic selection combined with instability.
Estimating effective population size from samples of sequences: a bootstrap Monte Carlo integration method
Authors: Felsenstein Joseph 
Published: September 2009

SummaryWe would like to use maximum likelihood to estimate parameters such as the effective population sizeNe, or, if we do not know mutation rates, the product 4Neμof mutation rate per site and effective population size. To compute the likelihood for a sample of unrecombined nucleotide sequences taken from a random-mating population it is necessary to sum over all genealogies that could have led to the sequences, computing for each one the probability that it would have yielded the sequences, and weighting each one by its prior probability. The genealogies vary in tree topology and in branch lengths. Although the likelihood and the prior are straightforward to compute, the summation over all genealogies seems at first sight hopelessly difficult. This paper reports that it is possible to carry out a Monte Carlo integration to evaluate the likelihoods pproximately. The method uses bootstrap sampling of sites to create data sets for each of which a maximum likelihood tree is estimated. The resulting trees are assumed to be sampled from a distribution whose height is proportional to the likelihood surface for the full data. That it will be so is dependent on a theorem which is not proven, but seems likely to be true if the sequences are not short. One can use the resulting estimated likelihood curve to make a maximum likelihood estimate of the parameter of interest,Neor of 4Neμ. The method requires at least 100 times the computational effort required for estimation of a phylogeny by maximum likelihood, but is practical on today's work stations. The method does not at present have any way of dealing with recombination.