bluuebunny/crossref_metadata_2025 huggingface dataset:
Fixation probability in spatially changing environments
Authors: Tachida Hidenori , Iizuka Masaru
Published: September 2009

The 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

Lines 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

The 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

An 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

Recessive 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

Recessive 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

Two 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

There 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

It 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

Levels 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

A 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

A 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

Genetic 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

Data 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

The 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

The 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

We 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.
Do Eve's Alleles Live On?
Authors: Watterson G. A. , Donnelly P.
Published: September 2009

Consider a random sample of genes at a locus, drawn from a population evolving according to the infinitely many, neutral, alleles model. The sample will have a most recent common ancestor gene, which we shall call ‘Eve’. The probability distribution, for the number of genes of oldest allelic type in a sample, is known and has a neat form. Rather less is known about the distribution for the number of genes in the sample which are of the same allelic type as Eve possessed. If the latter number is positive, then these genes are automatically of the oldest type in the sample. But Eve may have no non-mutant descendants in the sample; then, the oldest allele will be a mutant arising in a line of descent after Eve. The paper studies the number of non-mutant descendants from Eve, its distribution and moments. It seems that there may be few neat results. In large samples, the proportion of genes of Eve's type has an approximate β-like density, together with a discrete probability atom at zero, if the mutation rate parameter is low. Extinction of the allele of even the population's common ancestor is possible, but not certain, and bounds are obtained for its probability. Some comments are made about the applications and implications of the results for human mitochondrial DNA.
Mutation accumulation in finite outbreeding and inbreeding populations
Authors: Charlesworth D. , Morgan M. T. , Charlesworth B.
Published: September 2009

We have carried out an investigation of the effects of various parameters on the accumulation of deleterious mutant alleles in finite diploid populations. Two different processes contribute to mutation accumulation. In random-mating populations of very small size and with tight linkage, fixation of mutant alleles occurs at a high rate, but decreases with extremely tight linkage. With very restricted recombination, the numbers of low-frequency mutant alleles per genome in randommating populations increase over time independently of fixation (Muller's ratchet). Increased population size affects the ratchet less than the fixation process, and the decline in population fitness is dominated by the ratchet in populations of size greater than about 100, especially with high mutation rates. The effects of differences in the selection parameters (strength of selection, dominance coefficient), of multiplicative versus synergistic selection, and of different amounts of inbreeding, are complex, but can be interpreted in terms of opposing effects of selection on individual loci and associations between loci. Stronger selection slows the accumulation of mutations, though a faster decline in mean fitness sometimes results. Increasing dominance tends to have a similar effect to greater strength of selection. High inbreeding slows the ratchet, because the increased homozygous expression of mutant alleles in inbred populations has effects similar to stronger selection, and because with inbreeding there is a higher initial frequency of the least loaded class. Fixation of deleterious mutations is accelerated in highly inbred populations. Even with inbreeding, sexual populations larger than 100 will probably rarely experience mutation accumulation to the point that their survival is endangered because neither fixation nor the ratchet has effects of the magnitude seen in asexual populations. The effects of breeding system and rate of recombination on the rate of molecular evolution by the fixation of slightly deleterious alleles are discussed.
Meiotic drive on aberrant chromosome 1 in the mouse is determined by a linked distorter
Authors: Agulnik Sergei I. , Sabantsev Igor D. , Orlova Galina V. , Ruvinsky Anatoly O.
Published: September 2009

An aberrant chromosome 1 carrying an inverted fragment with two amplified DNA regions was isolated from wild populations ofMus musculus. Meiotic drive favouring the aberrant chromosome was demonstrated for heterozygous females. Its cause was preferential passage of aberrant chromosome 1 to the oocyte. Genetic analysis allowed us to identify a two-component system conditioning deviation from equal segregation of the homologues. The system consists of a postulated distorter and responder. The distorter is located on chromosome 1 distally to the responder, between thelnandPep-3genes, and it acts on the responder when intransposition. Polymorphism of the distorters was manifested as variation in their effect on meiotic drive level in the laboratory strain and mice from wild populations.
Effect of sperm genotype on chromatid segregation in female mice heterozygous for aberrant chromosome 1
Authors: Agulnik Sergei I. , Sabantsev Igor D. , Ruvinsky Anatoly O.
Published: September 2009

An aberrant chromosome 1 with two large homogeneously staining insertions was isolated from wild populations of Mus musculus musculus. The specific features of the aberrant chromosome have been described elsewhere (Agulnik et al. 1990). These include its preferential entry into the oocyte of heterozygous females, increased mortality of homozygotes and decreased fertility of homozygous females. Here we present data indicating that chromatid segregation in heterozygous females depends upon which sperm enters the oocyte before the second meiotic division: meioticdrive is powerful when it is sperm bearing normal chromosome 1, and segregation normalizesduring Mil when it is sperm bearing chromosome 1 with the extra segment. Experimental data are adduced and explanations offered for the observed phenomenon.
Group selection and the ‘shifting balance’
Authors: Rouhani S. , Barton N. H.
Published: September 2009

We investigate the establishment and spread of new adaptive peaks within Wright's ‘shifting balance’. The third phase of the ‘shifting balance’ involves a kind of group selection, since demes in which a superior peak has been established contain more individuals, and so send out more migrants. We assume that population size,N, increases with mean fitness,, according to the exponential relation,. Here,kis a measure of the weakness of density-dependent regulation, and equals the inverse of the regression of log (fitness) on log(N). In the island model, we find that just as with soft selection (k= 0), two distinct types of behaviour exist: group selection makes no qualitative difference. With low numbers of migrants, demes fluctuate almost independently, and only one equilibrium exists. With large numbers of migrants, all the demes evolve towards the same adaptive peak, and so the whole population can move towards one or other of the peaks. Group selection can be understood in terms of an effective mean fitness function. Its main consequence is to increase the effect of selection relative to drift (Ns), and so increase the bias towards the fitter peak. However, this increased bias depends on the ratio betweenkand the deme size (k/N), and so is very small when density-dependence is reasonably strong.
Evidence for aWolbachiasymbiont inDrosophila melanogaster
Authors: Holden Peter R. , Jones Peter , Brookfield John F. Y.
Published: September 2009

The bacterial cell division gene,ftsZ, was used as a specific probe to show the presence of a symbiotic bacterium in two wild type strains ofDrosophila melanogaster. Under stringent hybridization conditions we have shown that the bacterium is transferred to the progeny of these strains from infected mothers and can be eradicated by treatment with the antibiotic tetracycline. We have characterized this bacterium, by amplifying and sequencing its 16S rRNA gene, as being a member of the genus Wolbachia, an organism that is known to parasitize a range of insects includingDrosophila simulans. In a series of reciprocal crosses no evidence was found that the symbiont causes cytoplasmic incompatibility (CI) which is known to occur in infected strains ofD. simulans. The implications of these findings are discussed.
Parental origin of mutant allele does not explain absence of gene dose in X-linked Hyp mice
Authors: Qiu Z. Q. , Tenenhouse H. S. , Scriver C. R.
Published: September 2009

The expectation for a gene dose effect in an X-linked phenotype is that the corresponding metrical trait in heterozygous females will lie between values for affected hemizygous males and unaffected males and females. We made sequential measurements (at 30, 60, 90, 120 and 150 days) of serum phosphate concentration and tail length in mice with X-linked hypophosphatemia (genotypes: Hyp/Y, Hyp/+ and Hyp/Hyp) and in their normal litter-mates (genotypes: +/Y, +/+). We also measured renal mitochondrial 25-hydroxyvitamin D3-24-hydroxylase (24-hydroxylase) activity in 5 to 7-month-old mice fed control and low phosphate diets and representing all five genotypes. The animals were obtained by controlled breeding under uniform environmental conditions. The mutant animals all had uniformly and significantly lower serum phosphate levels, shorter tail length and higher 24-hydroxylase activity relative to unaffected litter-mates. There was no evidence of a gene dose effect because values were not significantly different among the three mutant genotypes. We also studied the influence of gamete of origin on serum phosphate, tail length and renal mitochondrial 24-hydroxylase activity in the Hyp/+ offspring of affected males (Hyp/Y) or affected females (Hyp/+ or Hyp/Hyp). We found no effect on the distribution of trait values. We conclude that parental origin of mutant allele does not explain the absence of a gene dose effect in Hyp mice.
Evolutionary effects of density-dependent selection in plants
Authors: Namkoong G. , Bishir J. , Roberds J. H.
Published: September 2009

The evolution of traits that affect genotypic responses to density regulated resources can be strongly affected by population dynamics in ways that are unpredictable from individual viability or reproduction potentials. Genotypes that are most efficient in utilizing energy may not always displace less efficient ones, and the evolution of energy allocation strategies may not always favour reproductive fitness because of their effects on destabilizing population growth rates. Furthermore, genetic polymorphisms in single loci that affect such traits can be maintained in populations with stable, periodic changes in population size and gene frequencies in the absence of heterozygote superiority. In fact, in the models investigated in this paper, the polymorphism is maintained, even in the absence of equilibrium genotypic frequencies.
Temperature related fertility selection on body size and the sex-ratio gene arrangement inDrosophila pseudoobscura
Authors: Gebhardt M. D. , Anderson W. W.
Published: September 2009

We measured temperature-dependent fertility selection on body size inDrosophila pseudoobscurain the laboratory. One hundred single females of each of the three karyotypes involving the ‘sexratio’ (SR) and the standard (ST) gene arrangement on the sex chromosome laid eggs at either 18 or 24°C. The experiment addressed the following hypotheses: (a) Fertility selection on body size is weaker at the higher temperature, explaining in part why genetically smaller flies appear to evolve in populations at warmer localities, (b) Homokaryotypic SR females are less fecund than homokaryotypic ST females, possibly mediated by the effect of body size on fertility, explaining the low frequencies of SR despite its strong advantage due to meiotic drive. The data were also expected to shed light on a mechanism for the evolution of plasticity of body size through fertility selection in environments with an unpredictable temperature regime. Hypothesis (a) was clearly refuted because phenotypically larger ST females had an even larger fertility surplus at the higher temperature and, more importantly, the genetic correlation between fertility and body size disappeared at the lower temperature. As to (b), we found that temperature affects fertility directly and indirectly through body size such that ST and SR females were about equally fecund at both temperatures, although different in size and size-adjusted fertility. We observed heterosis for both size and fertility, which might stabilize the polymorphism in nature. The reaction norms of body size to the temperature difference were steeper for ST females than for SR females, implying that fertility selection could change phenotypic plasticity of body size in a population. Selection on body size depended not only on the temperature, but also on the karyotypes, suggesting that models of phenotype evolution using purely phenotypic fitness functions may often be inadequate.
The mouse t complex distorter-3 (Tcd-3) locus and transmission ratio distortion
Authors: Silver Lee M. , Buck Christine
Published: September 2009

A novel central partialthaplotype was generated by screening for a recombination event between overlapping distal and proximal partial haplotypes. This haplotype contains just two elementsTcrtandTcd-3t—involved in thet-specific transmission ratio distortion phenotype. Breeding analysis of males that carry this chromosome provides evidence thatTcd-3is, indeed, a distorter locus and not a second responder. Furthermore, the data indicate that a single well-defined distorter locus is insufficient to overcome completely the self-destructive, low transmission ratio distortion phenotype expressed by the t allele at the t complex responder locus, although a small, but highly significant, effect was observed.
Artificial sexual selection alters allometry in the stalk-eyed flyCyrtodiopsis dalmanni(Diptera: Diopsidae)
Authors: Wilkinson Gerald S.
Published: September 2009

Selection for increased and decreased ratio of eye span to body length was exerted on male stalk-eyed flies (Cyrtodiopsis dalmanni) from Malaysia using replicate selected and unselected lines. Response to selection was symmetrical. After 10 generations high line male eye span increased to 1·3 body lengths while low line male eye span declined to 1·1 body lengths. Realized heritabilities for eye span to body length ratio, estimated using regressions of deviations from unselected controls on cumulative selection differentials, were greater than zero for all four selected lines with averageh2= 0·35 + 0·06. The static linear allometric relationship between eye span and body length diverged between selected lines and rotated among selected line males in the same direction as among males in other sexually dimorphic diopsid species. Crosses between lines after 13 generations of selection indicate that the genes which influence relative eye span combine additively and do not exhibit sex linkage or maternal effects. The genetic correlation between the sexes, 0·29 + 0·05 as estimated by the regression of female on male change in eye span, did not prevent sexual dimorphism in eye span from diverging between lines. These results suggest that the exaggerated eye span of maleC. dalmanni is maintainedby natural selection opposing sexual selection rather than by lack of or asymmetry in additive genetic variation. Furthermore, the variation in sexual dimorphism for eye span-body length allometry observed among extant diopsid species is consistent with sexual selection of variable intensity acting on relative eye span.
Population dynamics of DNA fingerprint patterns within and between populations
Authors: Jin Li , Chakraborty Ranajit
Published: September 2009

DNA fingerprint is a pattern of a variable number of bands (DNA fragments) with different sizes on a Southern gel for each individual, generated by one or many VNTR loci. Genetic divergence between individuals within and between populations can be studied in terms of number of shared bands between individuals. Using a population genetic model we show that the expectations of measures of genetic distance between populations based on band sharing data from DNA fingerprint patterns are functions of composite parametersM= 4Nv, and time of divergence (t) between populations, whereNis the effective size of the populations, and ν, the mutation rate. The expected genetic distance remains linear with time of divergence at least up toNgenerations as long as the average heterozygosity at the DNA fingerprint loci remains at or below 90%. Neither incomplete knowledge of the allele frequencies at each locus, nor the unknown number of loci underlying DNA fingerprint pattern, compromise these evolutionary dynamics of DNA fingerprint patterns. Applications of this theory to data on three human populations, and review of literature indicate that co-migration of alleles, and the presence of syntenic loci underlying the fingerprint pattern have little impact of the reliability of evolutionary conclusions from DNA fingerprint studies.
Genetic basis and evolution of species-specific courtship song in theDrosophila aurariacomplex
Authors: Tomaru Masatoshi , Oguma Yuzuru
Published: September 2009

The interpulse interval (IPI) of courtship song in theDrosophila aurariacomplex is the only parameter that is consistently species-specific among the several courtship elements examined within the complex. The genetic basis of the species-specific courtship song was examined by analysing the song of interspecific hybrids and of backcross progeny. IPI of all interspecific hybrids except two showed intermediate values, suggesting autosomal control of species-specific IPI. However, significant deviation for shorter IPI from midparent was found in thirteen out of 20 crosses. The chromosomal analysis betweenD. aurariaandD. biaurariarevealed that the two major autosomes had significantly large effects on IPI, but the sex chromosome and cytoplasm had no effect. Since no interaction was detected, it is concluded that each autosome acts additively in the determination of species-specific IPI. The common ancestors of theD. aurariacomplex may also have had autosomal control of IPI, which has been conserved during speciation in the complex.
Simulation of marker assisted selection in hybrid populations
Authors: Gimelfarb A. , Lande R.
Published: September 2009

A computer model is developed that simulates Marker Assisted Selection (MAS) in a population produced by a cross between two inbred lines. Selection is based on an index that incorporates both phenotypic and molecular information. Molecular markers contributing to the index and their relative weights are determined by multiple regression of individual phenotype on the markers. The model is applied to investigate the efficiency of MAS as affected by several factors including total number of markers in the genome, number of markers contributing to the index, population size and heritability of the character. It is demonstrated that selection based on genetic markers can effectively utilize the linkage disequilibrium between genetic markers and QTLs created by crossing inbred lines. Selection is more efficient if markers contributing to the index are re-evaluated each generation than if they are evaluated only once. Increasing the total number of markers in the genome as well as the number of markers contributing to the index does not necessarily result in a higher efficiency of selection. Moreover, too many markers may result in a weaker response to selection. Population size is shown to be the most important factor affecting the efficiency of MAS.
Effects of autosomal inversions on meiotic exchange in distal and proximal regions of the X chromosome in a natural population ofDrosophila melanogaster
Authors: Sniegowski Paul D. , Pringle Anne , Hughes Kimberly A.
Published: September 2009

We have investigated the interchromosomal effect of the naturally-occurring paracentric inversionsIn(2L)tandIn(3R)Pon meiotic recombination in two regions of the X chromosome inDrosophila melanogaster. Previous authors have suggested that the rate of recombination at the tip of the X chromosome may be substantially higher in some natural populations than values measured in the laboratory, due to the interchromosomal effect of heterozygous autosomal inversions. This suggestion was motivated by observations that transposable elements are not as common at the tip of the X chromosome as predicted by recent research relating reduced meiotic exchange to increased element abundance inD. melanogaster. We examined the effects of heterozygousIn(2L)tandIn(3R)Pon recombination at both the tip and base of the X chromosome on a background of isogenic major chromosomes from a natural population. Both inversions substantially increased the rate of recombination at the base; neither one affected recombination at the tip. The results suggest that the presence of inversions in the study population does not elevate rates of crossing over at the tip of the X chromosome. The relevance of these results to ideas relating transposable element abundance to recombination rates is discussed.
Phenotypic conversion of mating type specificity induced by transplantation of macronucleoplasm inParamecium caudatum
Authors: Hori Manabu , Takahashi Mihoko
Published: September 2009

According to the classical genetic analysis inParamecium caudatumby Tsukii & Hiwatashi (1983), the E mating type of each syngen is expressed when the cell bears alleles specific for syngen at theMtlocus. The O mating type is expressed when cells are homozygous for the null allele,mt, at theMtlocus. In suchmt/mtcells the O syngen specificity is determined by alleles at two other loci calledMAandMB. Inthe study reported here, macronucleoplasmic transplantation technique was used to test the above hypothesis. When macronucleoplasm of type E3(mating type E of syngen 3) was injected into a macronucleus of type O12(mating type O of syngen 12), some recipients changed to type E of the donor syngen but some others changed to type E of the recipient syngen. Thus, syngen specificity of donor macronucleoplasm controlling type E was converted into that of the recipients, even though the latter has no gene that controls type E. When this transformant expressing type E of the recipiexnt syngen was re-injected back into E of the other syngen, the expression of the converted mating type in some way continued in the recipient. This suggests that syngen specificity of geneMtof the donor was changed to that of the recipients by intersyngenic transplantation of macronucleoplasm. We also obtained results suggesting that the gene dosage ratio ofMttomtorMttoMAandMBmay be important for syngen specific expression of type E.
Mapping studies of the distal imprinting region of mouse Chromosome 2
Authors: Peters J. , Beechey C. V. , Ball S. T. , Evans E. P.
Published: September 2009

The known limits of the distal imprinting region of mouse Chromosome (Chr) 2 are defined by the breakpoints of the translocations T(2;8)2Wa, (T2Wa), and T(2;16)28H, (T28H), in distal H3, and proximal H4 respectively. We have shown that T2Wa and T(2;4)1Go, (T1Go), which has a breakpoint in central H3 map close toa, non-agouti.Ada, adenosine deaminase, lies very near the proximal boundary andRa, ragged, maps very close to the distal boundary, and is less than 0-2 cM from wasted,wst. From the current dataAdacan be taken as the proximal, andRaas the distal gene marker of the imprinting region on the linkage map. From consensus maps twenty three other markers, including fourteen genes, lie betweenAdaandRa, some of which may be useful in investigations of imprinting. Of the markers included in the study reported here, four,Ada,ls, lethal spotting,Raandwstlie or probably lie within the region but none display any evidence of imprinting. We suggest that recombination frequency is elevated in distal Chr 2, because in none of the crosses could the most closely linked marker be ordered in relation to the translocation breakpoint due to the high frequency of double crossovers.