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PubMed1994

[Genetic differentiation of three quantitative characters and natural populations of Drosophila melanogaster of Eastern Europe and Central Asia].

Variation in three quantitative traits (wing length, rate of development, and productivity) was assessed in natural populations of Drosophila melanogaster of Eurasia. Wing length was estimated in 16 populations of Eastern Europe, Caucasus, and Central Asia. It was shown to decrease in clinal fashion from northwest to southeast and was negatively correlated with temperature. No difference in developmental rate among three east European and three Central Asian populations was detected. Productivity was significantly higher in populations of eastern Europe as compared to those of Central Asia. Selective mechanisms of maintenance of clinal variation in natural Drosophila populations are discussed.

Adaptation, Physiological↗
PubMed1988

Genetic polymorphism of a lymphocyte protein (p75) with six different alleles studied by two-dimensional electrophoresis: qualitative and quantitative data.

The genetic polymorphism of a human lymphocyte protein (p75) was studied by two-dimensional electrophoresis within 17 families and, in addition, 22 unrelated individuals from Southern Germany, resulting in a total of approximately 100 individuals. The cytosolic and membrane proteins from cell lysates of phytohemagglutinin stimulated and [3H]leucine labeled lymphocytes were separated by two-dimensional electrophoresis. The p75 protein with an approximate molecular weight of 75,000 occurred in six variants with slightly different isoelectric points and/or apparent molecular weights. Three common variants (a, b, and c) and three rare variants (d, e and f) could be distinguished. Among the approximately 100 individuals studied we observed 15 different phenotypes, three homozygous (p75-a, -b, -c) and 12 heterozygous (p75-ab, -ac, -bc, -ad, -ae, -be, -bf, -cd, -ce, -cf, -de, -df) phenotypes. The genetics of the p75 protein variations was ascertained by family studies and quantitative computer analysis. We were able to show a Mendelian mode of inheritance of the variants within the families and a gene-dosage dependence of the protein spots in homozygous and heterozygous phenotypes. The data allowed us to assume a polymorphic protein p75 determined by six alleles on a autosomal gene locus. The allele frequencies were calculated from the phenotype distribution within 56 unrelated individuals. The gene frequencies of the three common alleles ranged between 0.38 and 0.22 and the gene frequencies of the three rare alleles ranged between 0.01 and 0.07.

Alleles↗
PubMed1998

Strategies to utilize marker-quantitative trait loci associations.

Marker-assisted selection holds promise because genetic markers provide completely heritable traits than can be measured at any age in either sex and that are potentially correlated with traits of economic value. Theoretical and simulation studies show that the advantage of using marker-assisted selection can be substantial, particularly when marker information is used, because normal selection is less effective, for example, for sex-limited or carcass traits. Assessment of the available information and its most effective use is difficult, but approaches such as crossvalidation may help in this respect. Marker systems are now becoming available that allow the high density of markers required for close associations between marker loci and trait loci. Emerging technologies could allow large numbers of polymorphic sites to be identified, practically guaranteeing that markers will be available that are in complete association with any trait locus. Identifying which polymorphism out of many that is associated with any trait will remain problematic, but multiple-locus disequilibrium measures may allow performance to be associated with unique marker haplotypes. This type of approach, combined with cheap and high density markers, could allow a move from selection based on a combination of "infinitesimal" effects plus individual loci to effective total genomic selection. In such a unified model, each region of the genome would be given its appropriate weight in a breeding program. However, the collection of good quality trait information will remain central to the use of these technologies for the foreseeable future.

Animals↗
PubMed1984

Comparisons of different sampling designs for the determination of genetic transmission mechanisms in quantitative traits.

The power provided by several sampling designs to detect segregation at a major locus was investigated in a simulation study using phenotypes constructed from a major-locus genotypic mean, a background polygenic effect, and an individual-specific environmental effect. Questions of which relatives, how many relatives, and how many independent pedigrees to collect were considered, using configurations ranging from nuclear families of size 5 to 4-generation pedigrees of size 45. Each configuration contained a single proband whose phenotype exceeded the 95th percentile in a population where 2.5% carry the disease susceptibility allele. Results suggest that, under the conditions simulated, when total sample size is fixed, samples composed of 3-generation pedigrees of intermediate size provide a greater magnitude of support for the presence of a major locus than do samples composed of nuclear families or 4-generation pedigrees. This study is the first to consider both the discriminatory power and estimation efficiency in comparing alternative sampling strategies for pedigree data.

Genetics, Medical↗
PubMed2026

Integrating Genetics and Environment to Find Causal Mechanisms for Multiple Sclerosis.

Genome-wide association studies (GWAS) have identified hundreds of risk loci for multiple sclerosis (MS), but we have limited knowledge of the mechanisms through which genetic variants mediate risk. Similarly, epidemiological studies implicate numerous environmental risk factors in MS risk, but these cannot identify specific causal mechanisms. We review our current knowledge of genetic mechanisms in MS, including the critical role of expression quantitative trait locus (eQTL) mapping in translating genetic risk loci into causal mechanisms. Molecular and functional context has emerged as an important missing component of these studies, and we discuss how environmental risk factors can be modelled in a quantitative genetic context to identify disease mechanisms. In parallel, we highlight recent advances in which quantitative genetic methods establish a causal role for low vitamin D and obesity in MS, and to dissect the mechanisms through which these operate. As genetic, transcriptional, and epigenetic studies continue to expand, further mechanistic insights for MS are likely to come from the integration of genetic and environmental data.

Humans↗
PubMed2005

Theories of adaptation: what they do and don't say.

Theoretical work on adaptation has lagged behind experimental. But two classes of adaptation model have been partly explored. One is phenotypic and the other DNA sequence based. I briefly consider an example of each--Fisher's geometric model and Gillespie's mutational landscape model, respectively--reviewing recent results. Despite their fundamental differences, these models give rise to several strikingly similar results. I consider possible reasons for this congruence. I also emphasize what predictions do and, as important, do not follow from these models.

Adaptation, Biological↗
PubMed2005

Testing hypotheses regarding the genetics of adaptation.

Many of the hypotheses regarding the genetics of adaptation require that one know specific details about the genetic basis of complex traits, such as the number and effects of the loci involved. Developments in molecular biology have made it possible to create relatively dense maps of markers that can potentially be used to map genes underlying specific traits. However, there are a number of reasons to doubt that such mapping will provide the level of resolution necessary to specifically address many evolutionary questions. Moreover, evolutionary change is built upon the substitution of individual mutations, many of which may now be cosegregating in the same allele. In order for this developing area not to become a mirage that traps the efforts of an entire field, the genetic dissection of adaptive traits should be conducted within a strict hypothesis-testing framework and within systems that promise a reasonable chance of identifying the specific genetic changes of interest. Continuing advances in molecular technology may lead the way here, but some form of genetic testing is likely to be forever required.

Adaptation, Biological↗
PubMed2006

Heritability of sperm length in the bumblebee Bombus terrestris.

Sperm length is highly variable, both between and within species, but the evolutionary significance of this variation is poorly understood. Sexual selection on sperm length requires a significant additive genetic variance, but few studies have actually measured this. Here we present the first estimates of narrow sense heritability of sperm length in a social insect, the bumblebee Bombus terrestris. In spite of a balanced and straightforward rearing design of colonies, and the possibility to replicate measurements of sperm within single males nested within colonies, the analysis proved to be complex. Several appropriate statistical models were derived, each depending on different assumptions. The heritability estimates obtained ranged from h (2) = 0.197 +/- 0.091 to h (2) = 0.429 +/- 0.154. All our estimates were substantially lower than previous estimates of sperm length heritability in non-social insects and vertebrates.

Analysis of Variance↗
PubMed2006

Quantitative structure analysis of genetic diversity among spring bread wheats (Triticum aestivum L.) from different geographical regions.

Genetic diversity in spring bread wheat (T. aestivum L.) was studied in a total of 69 accessions. For this purpose, 52 microsatellite (SSR) markers were used and a total of 406 alleles were detected, of which 182 (44.8%) occurred at a frequency of <5% (rare alleles). The number of alleles per locus ranged from 2 to 14 with an average of 7.81. The largest number of alleles per locus occurred in the B genome (8.65) as compared to the A (8.43) and D (5.93) genomes, respectively. The polymorphism index content (PIC) value varied from 0.24 to 0.89 with an average of 0.68. The highest PIC for all accessions was found in the B genome (0.71) as compared to the A (0.68) and D genomes (0.63). Genetic distance-based method (standard UPGMA clustering) and a model-based method (structure analysis) were used for cluster analysis. The two methods led to analogical results. Analysis of molecular variance (AMOVA) showed that 80.6% of the total variation could be explained by the variance within the geographical groups. In comparison to the diversity detected for all accessions (H ( e ) = 0.68), genetic diversity among European spring bread wheats was H ( e ) = 0.65. A comparatively higher diversity was observed between wheat varieties from Southern European countries (Austria/Switzerland, Portugal/Spain) corresponding to those from other regions.

Alleles↗
PubMed2006

Multi-species outcomes in a common model of sympatric speciation.

While models of sympatric speciation are motivated in part by multi-species adaptive radiations such as the Cameroon crater lake cichlids, existing models have focused on bifurcation into a single pair of daughter species. This paper shows that a familiar model of sympatric speciation, driven by intraspecific competition and assortative mating based on ecological characters values, can yield multiple daughter species if individual niche widths are sufficiently restricted. Surprisingly, the multi-species outcome is not produced by successive bifurcation events, but by simultaneous divergence resulting in a hard polytomy. This result is sensitive to a number of assumptions, whose violation may prevent speciation. In some cases when speciation fails, the population instead ends in a state that closely resembles incipient species pairs, with an ecological polymorphism and partial reproductive isolation. However, this polymorphism is stable and does not lead to complete reproductive isolation, suggesting that empirical cases of incipient species pairs may not always end in speciation.

Animals↗
PubMed2006

Beautiful parents have more daughters: a further implication of the generalized Trivers-Willard hypothesis (gTWH).

The generalized Trivers-Willard hypothesis (gTWH) [Kanazawa, S., 2005. Big and tall parents have more sons: further generalizations of the Trivers-Willard hypothesis. J. Theor. Biol. 235, 583-590) proposes that parents who possess any heritable trait which increases the male reproductive success at a greater rate than female reproductive success in a given environment will have a higher-than-expected offspring sex ratio, and parents who possess any heritable trait which increases the female reproductive success at a greater rate than male reproductive success in a given environment will have a lower-than-expected offspring sex ratio. One heritable trait which increases the reproductive success of daughters much more than that of sons is physical attractiveness. I therefore predict that physically attractive parents have a lower-than-expected offspring sex ratio (more daughters). Further, if beautiful parents have more daughters and physical attractiveness is heritable, then, over evolutionary history, women should gradually become more attractive than men. The analysis of the National Longitudinal Study of Adolescent Health (Add Health) confirm both of these hypotheses. Very attractive individuals are 26% less likely to have a son, and women are significantly more physically attractive than men in the representative American sample.

Beauty↗
PubMed2006

Discrete polymorphisms due to disruptive selection on a continuous trait--I: the one-locus case.

We have investigated, numerically and analytically, long-term evolution under frequency-dependent disruptive selection of a continuous trait varying in a finite range and controlled by one diploid mendelian locus. We found that evolution converges towards a unique long-term equilibrium where only two extreme phenotypes are present with frequencies identical to those of the mixed strategy that would be the unique ESS of the game defined by the basic fitness function of the model. As long as this precise phenotypic composition is preserved, any genetic configuration of the polymorphism is equally acceptable (selectively neutral) at the equilibrium. Thus the number of alleles and their dominance pattern may vary considerably among different equilibrium populations. If genetic expression of the trait is variable but the amount of variability is genetically modifiable, disruptive selection, acting on such modifiers, produces a steady increase of expression variability before the equilibrium is attained. In this case a population at the long-term equilibrium might even be genetically monomorphic, with the phenotypic dimorphism resulting from purely random individual variation.

Alleles↗
PubMed2006

Resolving the paradox of common, harmful, heritable mental disorders: which evolutionary genetic models work best?

Given that natural selection is so powerful at optimizing complex adaptations, why does it seem unable to eliminate genes (susceptibility alleles) that predispose to common, harmful, heritable mental disorders, such as schizophrenia or bipolar disorder? We assess three leading explanations for this apparent paradox from evolutionary genetic theory: (1) ancestral neutrality (susceptibility alleles were not harmful among ancestors), (2) balancing selection (susceptibility alleles sometimes increased fitness), and (3) polygenic mutation-selection balance (mental disorders reflect the inevitable mutational load on the thousands of genes underlying human behavior). The first two explanations are commonly assumed in psychiatric genetics and Darwinian psychiatry, while mutation-selection has often been discounted. All three models can explain persistent genetic variance in some traits under some conditions, but the first two have serious problems in explaining human mental disorders. Ancestral neutrality fails to explain low mental disorder frequencies and requires implausibly small selection coefficients against mental disorders given the data on the reproductive costs and impairment of mental disorders. Balancing selection (including spatio-temporal variation in selection, heterozygote advantage, antagonistic pleiotropy, and frequency-dependent selection) tends to favor environmentally contingent adaptations (which would show no heritability) or high-frequency alleles (which psychiatric genetics would have already found). Only polygenic mutation-selection balance seems consistent with the data on mental disorder prevalence rates, fitness costs, the likely rarity of susceptibility alleles, and the increased risks of mental disorders with brain trauma, inbreeding, and paternal age. This evolutionary genetic framework for mental disorders has wide-ranging implications for psychology, psychiatry, behavior genetics, molecular genetics, and evolutionary approaches to studying human behavior.

Adaptation, Physiological↗
PubMed2004

Effect of voluntary exercise on genetically obese Cpefat/fat mice: quantitative proteomics of serum.

OBJECTIVE: To compare the effect of voluntary exercise on body weight, food consumption, and levels of serum proteins between wild-type and carboxypeptidase E-deficient (Cpefat/fat) mice. RESEARCH METHODS AND PROCEDURES: Study 1 consisted of three groups of female mice: Cpefat/fat mice with continuous access to exercise wheels for 3 weeks (n = 4); wild-type C57BKS mice with access to exercise wheels for 3 weeks (n = 4); and sedentary Cpefat/fat mice (n = 3). Activity, body weight, and food consumption were monitored for this period and a subsequent 9-week period without exercise wheels. Study 2 consisted of four groups of male mice (n = 6 to 7 each): Cpefat/fat mice with exercise wheels, wild-type mice with exercise wheels, and Cpefat/fat and wild-type mice without exercise wheels. Body weight and food consumption were measured over 4 weeks. Sera were collected, and the protein profile was determined by 2-dimensional gel electrophoresis and mass spectrometry. RESULTS: Cpefat/fat mice were moderately hyperphagic but lost weight during the initial exercise period because of greater energy expenditure. The effect of exercise was temporary, and the mice gained weight after the second week. Several serum proteins were found to be altered by exercise: haptoglobin was decreased by exercise in Cpefat/fat mice, and several kallikreins were increased by exercise in wild-type mice. DISCUSSION: The access to exercise wheels provided an initial weight loss in Cpefat/fat mice, but this effect was offset by elevated food consumption. The serum proteomics results indicated that Cpefat/fat and wild-type mice differed in their response to exercise.

Adipose Tissue↗
PubMed2001

Heritability of morphological traits in Darwin's finches: misidentified paternity and maternal effects.

We studied the influence of extra-pair paternity on heritability estimates of morphological traits in a population of the Medium Ground Finch (Geospiza fortis) on Isla Daphne Major, Galápagos. Data from eight microsatellite loci were used to determine parentage. Six morphological traits measured on each finch were represented by two separate principal components analyses, one for the three bill measurements and one for the body size measurements. Heritabilities were calculated using weighted regressions of offspring on their parents and also offspring on their grandparents. We found that 20% of all offspring were extra-pair young but all offspring matched their mothers. Heritabilities derived from midparent-offspring regressions were all high and significantly different from zero. Removing all extra-pair young from the data set increased father-offspring regressions by an average of 21%, but mother-offspring resemblance still exceeded father-offspring resemblance by up to 42%. These results and grandparent-offspring regressions provide evidence for maternal effects, comparable in magnitude to those reported in other studies of wild birds.

Animals↗
PubMed2003

Quantitative analysis of GAL genetic switch of Saccharomyces cerevisiae reveals that nucleocytoplasmic shuttling of Gal80p results in a highly sensitive response to galactose.

The nucleocytoplasmic shuttling of the repressor Gal80p is known to play a pivotal role in the signal transduction process of GAL genetic switch of Saccharomyces cerevisiae (Peng, G., and Hopper, J. E. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 8548-8553). We have developed a comprehensive model of this GAL switch to quantify the expression from the GAL promoter containing one or two Gal4p-binding sites and to understand the biological significance of the shuttling process. Our experiments show that the expression of proteins from the GAL promoter containing one and two binding sites for Gal4p is ultrasensitive (a steep response to a given input). Furthermore, the model revealed that the shuttling of Gal80p is the key step in imparting ultrasensitive response to the inducer. During induction, free Gal80p concentration is altered by sequestration, without any change in the distribution coefficient across the nuclear membrane. Furthermore, the estimated concentrations of Gal80p and Gal3p allow basal expression of alpha-galactosidase, but not beta-galactosidase, from the GAL promoter containing one and two binding sites for Gal4p, respectively. Conversely, the expression from genes with two binding sites is more sensitive to inducer concentration as compared with one binding site. We show that autoregulation of Gal80p is coincidental to the autoregulation of Gal3p, and it does not impart ultrasensitivity. We conclude from our analysis that the ultrasensitivity of the GAL genetic switch is solely because of the shuttling phenomena of the repressor Gal80p across the nuclear membrane.

Cell Nucleus↗
PubMed1973

A quantitative analysis of the genetics of resting blood lactic acid levels in mice.

Resting blood lactate levels were measured in inbred mouse strains, their F(1), and several of their segregating generations to determine whether the level of lactic acid is influenced by genetic factors. The inbred strains in each of the two sets used differed significantly from one another for this character. Only one strain showed a significant sex difference. The data could not be fully analyzed because of the failure to fulfill Mather's first criterion for an adequate scale. Nonallelic interactions, in particular, additive x dominance and dominance x dominance, were found to influence the generation means. Genotype x environment interaction was detected and eliminated by log transformation. Negative heterosis was exhibited by all but one noninbred generation.-The data suggest that genes influencing the character are dispersed between the parental lines and that interactions are predominantly of the duplicate kind. A buffering system by which lactate levels are kept at a minimum is proposed.

Analysis of Variance↗