bluuebunny/crossref_metadata_2025_split huggingface dataset:
Jumping genes meet abdominal bristles: hybrid dysgenesis-induced quantitative variation inDrosophila melanogaster
Authors: Mackay Trudy F. C. 
Published: September 2009

SUMMARYWhen males from a strain ofDrosophila melanogasterwhich have multiple copies of the P family of transposable elements integrated into their genome (Bingham, Kid well & Rubin, 1982) (‘P’ strains) are crossed to females of strains lacking those elements (‘M’ strains), the F1 progeny manifest a number of aberrant traits known collectively as hybrid dysgenesis (Kidwell, Kidwell & Sved, 1977). Progeny of the reciprocal cross (P♀ × ♂M) are normal. The dysgenic syndrome is characterized by a high degree of genomic instability caused by enhanced transposition of P elements. Since mutations at visible loci and chromosomal rearrangements are frequently observed in dysgenic hybrids, it was hypothesized that this phenomenon could be used to investigate the effects of transposition on quantitative characters; therefore, the progeny of dysgenic and non-dysgenic crosses were artificially selected for high and low abdominal bristle number. The response to selection, phenotypic variation, and realized heritability were all increased in the dysgenic lines, relative to the non-dysgenic control. It is postulated that these features are the result of P element-induced mutations of loci affecting bristle number, and that future work should lead to the identification of these loci, as well as elucidating the role of transposition in population differentiation for metric traits
Hybrid dysgenesis inDrosophila melanogaster: the evolution of mixedPandMpopulations maintained at high temperature
Authors: Kiyasu Phillip K. , Kidwell Margaret G. 
Published: September 2009

SUMMARYThe ability of hybrid dysgenesisPfactors to survive and multiply under conditions of strong negative sterility selection was studied in mixedPandMlaboratory cultures. Eight populations were initiated with varying proportions ofPandMstrains. Mixed populations and controls were maintained for seventeen generations at 27 °C, a temperature sufficiently high to induce maximum frequencies of sterility in dysgenic hybrids. The two components of dysgenesis,Pfactor activity and cytotype, were monitored every generation for the first ten generations and intermittently thereafter. With one exception, all the mixed populations evolved to thePtype indicating thatPfactors can survive and multiply, despite low initial frequency and strong negative selection against dysgenic hybrids. However, the average level ofPfactor activity attained at equilibrium was considerably lower than that of thePstrain control population maintained under the same conditions. It was also lower than the equilibrium level ofPfactor activity attained in a similar experiment carried out at a lower temperature, suggesting that selection favouredPfactors with weak rather than strong sterility potential.
The angora locus (go) in the mouse: hair morphology, duration of growth cycle and site of action
Authors: Pennycuik Pamela R. , Raphael Kathryn A. 
Published: September 2009

SUMMARYAll four coat hair types were longer in mice homozygous for angora (go / go) than in wild-type mice ( + / +). This increase in hair length in mutant animals was due to an increase in the duration of the phase of hair growth (anagen VI). When skin recombinants incorporating mutant or wild-type epidermis and dermis were grafted to a nude host, the activity of the mutant was found to be confined to the epidermis.
The population genetics of haplo-diploids and X-linked genes
Authors: Avery P. J. 
Published: September 2009

SUMMARYFrom the available electrophoretic data, it is clear that haplodiploid insects have a much lower level of genetic variability than diploid insects, a difference that is only partially explained by the social structure of some haplodiploid species. The data comparingX-linked genes and autosomal genes in the same species is much more sparse and little can be inferred from it. This data is compared with theoretical analyses ofX-linked genes and genes in haplodiploids. (The theoretical population genetics ofX-linked genes and genes in haplodiploids are identical.)X-linked genes under directional selection will be lost or fixed more quickly than autosomal genes as selection acts more directly onX-linked genes and the effective population size is smaller. However, deleterious disease genes, maintained by mutation pressure, will give higher disease incidences atX-linked loci and hence rare mutants are easier to detect atX-linked loci. Considering the forces which can maintain balanced polymorphisms, there are much stronger restrictions on the fitness parameters atX-linked loci than at autosomal loci if genetic variability is to be maintained, and thus fewer polymorphic loci are to be expected on theX-chromosome and in haplodiploids. However, the mutation-random drift hypothesis also leads to the expectation of lower heterozygosity due to the decrease in effective population size. Thus the theoretical results fit in with the data but it is still subject to argument whether selection or mutation-random drift are maintaining most of the genetic variability atX-linked genes and genes in haplodiploids.
A simple method for increasing the response to artificial selection
Authors: Toro Miguel Angel , Nieto Blanca Maria 
Published: September 2009

SUMMARYSelection theory usually assumes an equally probable contribution of each selected individual to a large ‘gene pool’ from which the individuals to be measured in the next generation are sampled. With unequal contributions it is possible to find several sets of values for N (the number of selected individuals) and fi (probability of contribution of the ith individual) such that the same selection intensity is attained. It is suggested that the set of values producing minimum genetic drift should be chosen in order to increase the long-term response without any reduction in the short-term advance.
Adaptation to environmental heterogeneity in populations ofDrosophila melanogaster
Authors: Verdonck Margriet V. 
Published: September 2009

SummaryFor 29 generations, populations ofDrosophila melanogasterwere offered one favourable (standard) and one suboptimal (salt-supplemented) medium, either singly or simultaneously. Egg-to-adult viability, fecundity and choice of oviposition medium were measured at regular intervals on both resources up to 17 generations after initiation of the salt treatment. Except for a decrease in viability on salt medium in the single-resource populations (SRPs) maintained on the optimal medium, these fitness components remained unchanged. Estimation of a more inclusive measure of fitness, productivity, obtained at generations 27–29, revealed that: (1) the SRPs maintained on salt medium were more adapted to salt medium; (2) the mixed-resource populations (MRPs) were intermediate in their adaptation to salt medium between either type of single-resource population. These results support Levins' model of optimal strategy for populations living in a coarse-grained environment when the fitness set is convex. Family selection for increased and decreased resistance to salt in the medium, carried out for the viability component at generations nine and 19, showed that: (1) genetic variation with respect to this component was present in all populations; (2) the SRPs maintained on salt medium had responded to the salt treatment by eliminating sensitive genotypes; (3) in the first selection experiment, the MRPs had a greater amount of additive genetic variance with respect to viability than either type of SRP; in the second experiment, this difference was not significant, but it was in the predicted direction. The latter finding provides some evidence in favour of the hypothesis repeatedly presented in the literature that environmental heterogeneity could promote the maintenance of genetic variability in populations.
Interspecific mitochondrial DNA transfer and the colonization of Scandinavia by mice
Authors: Gyllensten Ulf , Wilson Allan C. 
Published: September 2009

SummaryRestriction enzymes were used to search for genetic variability at 162 cleavage sites in mitochondrial DNA (mtDNA) purified from 22 mice caught at seven Swedish localities. Although all of these mice bear the nuclear genes ofMus musculus, they bear the mtDNA ofM. domesticusexclusively. Yet, some of the Swedish localities are 750 km away from the hybrid zone between these two species. Furthermore, only one type of mtDNA was found at the seven Swedish localities; this type was found before at an eighth locality in Sweden as well as in Jutland north of the hybrid zone. The apparent lack of mtDNA divergence in the mouse population of Sweden contrasts with the extensive divergence usually found within other geographic areas in Europe, Africa and North America. Electrophoretic analysis of proteins encoded by nuclear genes indicates that the Swedish mice have lower average heterozygosity than Danish and Central European populations ofmusculusmice. These findings lead us to suggest that the source of the commensal mouse population in Sweden was a small propagule that originated from a population situated only a few kilometres to the east of the point at which the hybrid zone on the European mainland meets the Baltic Sea, namely on East Holstein. Such a founder event may have been associated with the spread of farming from north Germany into Sweden about 4000 years ago.
A test for the role of natural selection in the stabilization of transposable element copy number in a population ofDrosophila melanogaster
Authors: Montgomery Elizabeth , Charlesworth Brian , Langley Charles H. 
Published: September 2009

SummaryThe numbers of members of three families ofcopia-like elements were counted on twentyX, 2nd and 3rd chromosomes collected from a natural population ofDrosophila melanogaster. Theoretical predictions were computed for two models of copy number stabilization: (1) element frequencies are regulated by a simple genetic process such as copy number dependent transposition or excision, independent of chromosomal location; (2) elements are eliminated by natural selection against mutational effects of their insertion into the chromosome. Since insertions into theXcan be expected to suffer more selection than autosomal insertions, due to expression of mutant phenotypes in the hemizygous state, hypothesis 2, called the disproportional model, predicts that the proportion of elements on theXwill be smaller than the proportion of the genome contributed by theX, while hypothesis 1, called the equiproportional model, predicts that this proportionality will be unaffected. Two of the elements,297androo, showed no evidence for deficiency ofX-linked elements, but the data for a third element,412, were consistent with the prediction based on the selective model.These results indicate that simple selection against mutational effects of insertions of transposable elements is not generally adequate to account for their distribution within populations. We argue that a mechanism such as recombination between elements at different chromosomal sites, leading to rearrangements with highly deleterious, dominant effects could play a role in stabilizing copy number. This process would lead to a higher abundance of elements in genomic regions with restricted crossing over. We present some data indicating such an effect, and discuss possible interpretations.
Susceptibility to phenytoin-induced cleft lip with or without cleft palate: many genes are involved
Authors: Karolyi I. Jill , Liu Sharon , Erickson Robert P. 
Published: September 2009

SummaryIn a search for genetic differences in susceptibility to cleft lip with or without cleft palate [CL(P)], congenic and recombinant inbred strains of mice were treated with phenytoin or control injections. Of six loci tested, five were found to affect susceptibility to phenytoin-induced and/or sporadic CL(P): (1) the major histocompatibility locus,H-2; (2) the locus controlling β2-microglobulin,B2m; (3) a locus controlling β-glucuronidase,Gus; (4) the locus controllingN-acetyl transferase,Nat; and (5) the locus for brown pigmentation,b. B2mandGusonly affected the sporadic incidence of CL(P), while theblocus only affected phenytoin-induced incidence of CL(P). Three of these loci are also known to affect glucocorticoid-induced isolated cleft palate (CP), but different alleles of the loci are involved. Phenytoin did not affect levels of adenosine 3′,5′-cyclic monophosphate (cAMP) in palates and tongues of day 15 fetuses. A comparison of glucocorticoid receptor parameters with the incidence of phenytoin-induced CL(P) found no correlation.
Five of the nine genetically defined regions of mousethaplotypes are involved in transmission ratio distortion
Authors: Silver Lee M. , Remis David 
Published: September 2009

SummaryMousethaplotypes have been divided into nine subregions that are each defined by one or more molecular markers. In previous studies, three of these subregions were shown to contain ‘distorter loci’ that interact to effect the transmission-ratio distortion phenotype characteristic of all completethaplotypes. To determine which of the remaining six subregions also play a role in this phenotype, we analysed the accumulated data on transmission ratio distortion from males that carried one of 26 different combinations of two partialthaplotypes. We have obtained evidence for the association of two additional subregions with distorter loci. First, we present further evidence for the existence of a previously postulated distorter locus,Tcd-3, and describe its mapping to the T66C subregion. Secondly, we describe the identification of a new distorter locus,Tcd-4, in association with the subregion defined by the structural gene for theTCP-1 protein. Further studies indicate that two doses of theTcd-4locus are equivalent in effect to a single dose each ofTcd-4and a second distorter locus,Tcd-1. This result suggests that different distorter locus products could have a common mode of action.
A new regulatory gene in the histidine decarboxylase gene complex determines the responsiveness of the mouse kidney enzyme to testosterone
Authors: Middleton Richard J. , Martin S. A. M. , Bulfield Grahame 
Published: September 2009

SummaryThe level of histidine decarboxylase in mouse kidney normally differs between the sexes with females higher than males. In a strain derived from feral Danish mice (DAN), however, both males and females have the same, high, HDC activity due to the males being insensitive to repression by testosterone. Genetic analysis indicates that this insensitivity is caused by a variant allele of a new gene in the histidine decarboxylase gene complex,Hdc-a; theHdc-aballele in C57BL/10 confers high sensitivity to testosterone whereas theHdc-awallele in the DAN strain confers low sensitivity. In addition, the DAN strain has a novel haplotype for the other three known elements of [Hdc]: the alleleHdc-sdof the structural gene, theHdc-cdallele of the gene determining enzyme concentration, and the oestrogen-inducible alleleHdc-eb.
The general relationship between average effect and average excess
Authors: Templeton Alan R. 
Published: September 2009

SummaryThe average effect and average excess both measure the phenotypic effects of gametes in a population. A matrix notation is introduced that provides a general analytical solution for the average effects at a single locus with k alleles that can be solved for any population regardless of its genotype frequencies. This same notation also provides an easy way of deriving and generalizing to k alleles the well-known relationships between average effects and average excesses that exist under random-mating and regular deviations from Hardy–Weinberg equilibrium due to inbreeding.
Genetic localization of a regulatory site necessary for the production of the glue protein P5 inDrosophila melanogaster
Authors: Hoshizaki Deborah K. , Dlott Bonnie M. , Joslyn Geoffrey L. , Beckendorf Steven K. 
Published: September 2009

SummaryThe glue proteins are products of a developmentally regulated gene family. These genes are transcriptionally active during the third larval instar and code for the major protein products of salivary glands. The activity of several of the genes can be visualized as intermoult puffs in the polytene salivary gland chromosomes. The amount of one of these proteins, P5, varies widely among wild-type strains. We have used biochemical and genetic methods to investigate the source of this variation. The results ofin vitrotranslation of salivary gland RNA suggest that the variation occurs pretranslationally. Genetic mapping experiments showed that sites on several chromosomes can modulate the amount of P5, but that one site on the third chromosome determines the absence and presence of this protein. We have mapped this glue protein gene, calledGP5, to the interval betweenbx(3–58·8) and sr (3–62·0) which also includes the intermoult puff at 90BC. We discuss the relationship between P5 and the glue protein geneSgs-5which is also located at 90BC.
Transposition of the I element andcopiain a natural population ofDrosophila melanogaster
Authors: Leigh Brown Andrew J. , Moss Julie E. 
Published: September 2009

SummaryIn order to increase our understanding of the evolutionary dynamics of transposable genetic elements we have studied the chromosal location of copies of 2 element families in 20 X chromosomes extracted from a natural population ofDrosophila melanogasterfrom Spain. The I element was localized at a total of 64 chromosomal sites andcopiaat 45 sites in this sample with a mean copy number of 3·2 and 2·3 elements/chromosome respectively. Both elements were highly variable in location, with no site reaching a higher frequency than 4/20 in either case. Comparisons with other data sets suggest that insertion frequencies can be used to detect population structuring.
Evolution of genetic variability in a spatially heterogeneous environment: effects of genotype–environment interaction
Authors: Via Sara , Lande Russell 
Published: September 2009

SummaryClassical population genetic models show that disruptive selection in a spatially variable environment can maintain genetic variation. We present quantitative genetic models for the effects of disruptive selection between environments on the genetic covariance structure of a polygenic trait. Our models suggest that disruptive selection usually does not alter the equilibrium genetic variance, although transient changes are predicted. We view a quantitative character as a set ofcharacter states, each expressed in one environment. The genetic correlation between character states expressed in different environments strongly affects the evolution of the genetic variability. (1) If the genetic correlation between character states is not ± 1, then the mean phenotype expressed in each environment will eventually attain the optimum value for that environment; this is the evolution of phenotypic plasticity (Via & Lande, 1985). At the joint phenotypic optimum, there is no disruptive selection between environments and thus no increase in the equilibrium genetic variability over that maintained by a balance between mutation and stabilizing selection within each environment. (2) If, however, the genetic correlation between character states is ± 1, the mean phenotype will not evolve to the joint phenotypic optimum and a persistent force of disruptive selection between environments will increase the equilibrium genetic variance. (3) Numerical analyses of the dynamic equations indicate that the mean phenotype can usually be perturbed several phenotypic standard deviations from the optimum without producing transient changes of more than a few per cent in the genetic variances or correlations. It may thus be reasonable to assume a roughly constant covariance structure during phenotypic evolution unless genetic correlations among character states are extremely high or populations are frequently perturbed. (4) Transient changes in the genetic correlations between character states resulting from disruptive selection act to constrain the evolution of the mean phenotype rather than to facilitate it.
Genetic analysis of a large autosomal region inCaenorhabditis elegansby the use of a free duplication
Authors: Howell A. M. , Gilmour S. G. , Mancebo R. A. , Rose A. M. 
Published: September 2009

SummaryIn this paper we describe the use of a free duplication,sDp2(I;f), for the recovery, maintenance, and analysis of mutations defining essential genes in the left third of Linkage GroupIofCaenorhabditis elegans. The lethals were induced in a strain of genotype (sDp2) + /dpy-5+unc-13/dpy-5 unc-15+, using either 12 mM ethylmethane sulphonate or 1500 r of gamma radiation. Lethal mutations linked to thedpy-5 unc-13chromosome were recognized by the absence of Dpy-5 Unc-13 individuals amongst the self progeny and were maintained by isolating Unc-13 hermaphrodites. These strains – which have two mutant alleles of the essential gene and a wild-type allele on the duplication – are balanced, since crossing-over does not occur betweensDp2and the normal homologues. Using this sytem we have recovered 58 EMS-induced mutations. These have been characterized with regard to map position and complementation. Twenty-nine of the EMS-induced mutations lie to the left ofdpy-5and define 20 complementation groups; 3 were inseparable fromdpy-5and define 3 complementation groups; 21 were to the right and define 17 complementation groups. Among a set of 29 gamma radiation-induced lethal mutations, 17 appear to be single gene mutations or are very small deletions. We estimate that we have identified from one-sixth to one-half of the essential genes in thesDp2region.
Inheritance of seasonal cycles in Chrysoperla (Insecta: Neuroptera)
Authors: Tauber Catherine A. , Tauber Maurice J. 
Published: September 2009

SummaryTwo separate, but interacting, genetic systems underlie the variation in seasonal cycles among members of the Chrysoperla carnea species-complex. The two systems are expressed as all-or-none reproductive responses to photoperiod and prey (i.e. short-day/long-day requirement for reproduction versus long-day reproduction and prey requirement for reproduction versus reproduction without prey). In each case the alternative to reproduction is reproductive diapause. The photoperiodic responses are determined by alleles at two unlinked autosomal loci. The expression of dominance by the alleles at these loci varies among geographical populations. The genes that determine the photoperiodic responses also act as suppressors of the genes that govern responsiveness to prey. An autosomal, polygenic system, with a threshold for the expression of diapause, determines responsiveness to prey. The two genetic systems are important to seasonal diversification and speciation within the C. carnea species-complex.
Transposable element-induced polygenic mutations inDrosophila melanogaster
Authors: Mackay Trudy F. C. 
Published: September 2009

SummaryP-element mutagenesis was used to contaminate M-strain second chromosomes with P elements. The effect of P-element transposition on abdominal and sternopleural bristle scores and on female productivity was deduced by comparing the distributions of these quantitative traits among the contaminated second-chromosome lines with a control population of M-strain second-chromosome lines free of P elements. Estimates of P-element-induced mutational variance,Vm, for these characters are very high, and mutational ‘heritabilities’ (Vm/Ve, the ratio of mutational variance to environmental variance) are of the same order as heritabilities of these traits from natural populations. P-element-induced mutational variance of abdominal bristle score is roughly two orders of magnitude greater than spontaneous and X-ray-inducedVm/Vefor this trait.