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The genetic basis of fitness traits has been studied widely in animals, yet the contribution of genetic variation to these traits in humans is controversial. In particular, it is difficult to disentangle genetic versus environmental effects on fertility, because of within-family correlations of sociocultural, economic, and other non-genetic factors that influence family sizes. In this study, we investigated the genetic architecture of reproductive fitness traits in a fertile human population whose communal lifestyle assures uniform and equal access to resources. Our study revealed significant heritabilities for reproductive traits in both men and women, after accounting for common household effects shared among siblings and demographic changes in reproductive practices. Furthermore, our results indicate that both autosomal and X-linked additive and dominance variances contribute to these traits. We therefore propose that reproductive traits should be amenable to genetic mapping studies, and the results we present here will facilitate the search for the novel genes influencing natural fertility in humans. life history traits | human fertility doi/ 10.1073/pnas.0906196106

The assumption that different genetic elements can make separate contributions to the same quantitative trait was originally made in order to reconcile biometry and Mendelism and ever since has been used in population genetics, specifically for the trait of fitness. Here we show that sex is responsible for the existence of separate genetic effects on fitness and, more generally, for the existence of a hierarchy of genetic evolutionary modules. Using the tools developed in the process, we also demonstrate that in terms of their fitness effects, separation and fusion of genes are associated with the increase and decrease of the recombination rate between them, respectively. Implications for sex and evolution theory are discussed. recombination | epistasis | additive effects | fitness | genetic architecture doi/ 10.1073/pnas.0910734106

In old age, cognitive and physical functions are correlated. Knowing the correlations between genetic and environmental influences underlying this correlation can help to clarify the reasons for the observable (phenotypic) correlation. We estimated these correlations in a sample of 1,053 pairs of twins from the Longitudinal Study of Aging Danish Twins. Cognitive function was measured using forward and backward digit span, immediate and delayed memory, and fluency tasks. Physical function was measured using self-report of ability to carry out physical activities including walking, running, and climbing stairs. The phenotypic correlation between latent variable representations was .46 [95% confidence interval 0.27-0.65). The genetic correlation was .56 (95% confidence interval 0.15-1.00) and the nonshared environmental correlation .48 (95% confidence interval 0.35-0.61). We discuss several ways of interpreting these correlations. Key Words: Genetic and environmental correlation--Late-life cognitive ability--Physical fitness.

The distribution of fitness effects of new mutations is a fundamental parameter in genetics. Here we present a new method by which the distribution can be estimated. The method is fairly robust to changes in population size and admixture, and it can be corrected for any residual effects if a model of the demography is available. We apply the method to extensively sampled single-nucleotide polymorphism data from humans and estimate the distribution of fitness effects for amino acid changing mutations. We show that a gamma distribution with a shape parameter of 0.23 provides a good fit to the data and we estimate that >50% of mutations are likely to have mild effects, such that they reduce fitness by between one one-thousandth and one-tenth. We also infer that

Physical health has been linked consistently with both income and sense of control, and the authors previously demonstrated that genetic variation in physical health measures decreased with increasing income (see W. Johnson & R. F. Krueger, 2004). Using a nationwide sample of 719 twin pairs from the MacArthur Foundation National Survey of Midlife Development in the United States, in this study the authors show that genetic variation in physical health measures (number of chronic illnesses and body mass index) also decreases with increasing sense of control. The authors integrate findings for income and control by demonstrating an interaction between genetic influences on sense of control and income in explaining physical health. They hypothesize that the mechanism underlying the interaction is the known biological relationship between metabolic efficiency and adaptation to stressful environments.

Genetic research shows that pig coronary resistance arteries will respond to the enzyme reverse transcriptase polymerase chain reaction in coronary resistance experiments. Cell-specific messenger ribonucleic acid expression and enzyme endothelial cell nitric oxide synthase (ecNOS) expression is established. More ecNOS is expressed after endurance exercise.

The idea of inclusive fitness gives an important shortcut for studying social behavior and understanding how to apply it, assuming, however, that we can ignore the genetics underlying a particular trait. Researchers should avoid speaking about the inclusive fitness of individuals and speak only of the inclusive fitness of traits or strategies, or of the inclusive fitness of individuals for some particular trait.

Background. Functional abilities vary widely among elderly persons. The determinants of this variation are probably multiple and include normal aging processes as well as disease expression. This study estimates the relative importance of genetic and environmental factors to variation in functional abilities in elderly persons. Methods. We conducted a survey among all Danish twins aged 75 years and older who were identified in the population-based Danish Twin Registry. Interviews were conducted with 77% (7% by proxy responders) of the 3099 individuals in the study population. Functional abilities were assessed by validated Danish survey instruments and were scored on three scales. Heritability (proportion of the population variance attributable to genetic variation) was estimated using structural equation analyses. Results. Structural equation analyses revealed a substantial heritability (34%-47%) for the three functional ability scores among the women aged 80 years and older compared with a more modest heritability (15%-34%) among the women aged 75-79 years. The remaining variation could be attributed to individuals' nonfamilial environments. Comparisons of the functional abilities of twins with living versus deceased co-twins also suggested a difference in the genetic influence for the two age groups. Although heritability estimates were uniformly low in the male participant sample, the size of the sample was not sufficiently large to allow for precise estimates of heritability. Conclusion. For women we found that the effect of genetic factors on functional abilities increases with age and accounts for one third to one half of the variation among individuals aged 80 years and older. An understanding of the genetic mechanisms underlying functional abilities in the oldest individuals may enhance the possibilities for improving health in the elderly population by modifying environmental factors.

Would-be dopers may have a new target: the Rev-erb-a protein. Known to regulate sugar and fat metabolism, the nuclear receptor has now been linked to the production and function of [...]

New research shows that human physical performance is enhanced by a polymorphism in the gene that encodes angiotensin-converting enzyme. The research finds that the I (insertion) allele of the gene is linked with improved endurance among high-altitude mountaineers. It is suggested that the improved performance may result from variable increases in substrate delivery because of increased muscle capillary density and higher cardiac output.