Does education reduce the probability of being overweight?

This paper analyses the causal effect of education on the probability of being overweight by using longitudinal data of Australian identical twins. The data include self-reported and clinical measures of body size. The prevalence of overweight and obesity is growing rapidly in many countries. Education policies might be important for reducing this increase. Our cross-sectional estimates confirm the well-known negative association between education and the probability of being overweight. For men we find that education also reduces the probability of being overweight within pairs of identical twins. The estimated effect of education on overweight status increases with age. Remarkably, for women we find no negative effect of education on body size when fixed family effects are taken into account. Identical twin sisters that differ in educational attainment do not systematically differ in body size. This finding is robust to differences in employment and number of children.

Embracing polygenicity: a review of methods and tools for psychiatric genetics research.

The availability of genome-wide genetic data on hundreds of thousands of people has led to an equally rapid growth in methodologies available to analyse these data. While the motivation for undertaking genome-wide association studies (GWAS) is identification of genetic markers associated with complex traits, once generated these data can be used for many other analyses. GWAS have demonstrated that complex traits exhibit a highly polygenic genetic architecture, often with shared genetic risk factors across traits. New methods to analyse data from GWAS are increasingly being used to address a diverse set of questions about the aetiology of complex traits and diseases, including psychiatric disorders. Here, we give an overview of some of these methods and present examples of how they have contributed to our understanding of psychiatric disorders. We consider: (i) estimation of the extent of genetic influence on traits, (ii) uncovering of shared genetic control between traits, (iii) predictions of genetic risk for individuals, (iv) uncovering of causal relationships between traits, (v) identifying causal single-nucleotide polymorphisms and genes or (vi) the detection of genetic heterogeneity. This classification helps organise the large number of recently developed methods, although some could be placed in more than one category. While some methods require GWAS data on individual people, others simply use GWAS summary statistics data, allowing novel well-powered analyses to be conducted at a low computational burden

Dissection of genetic variation and evidence for pleiotropy in male pattern baldness.

Male pattern baldness (MPB) is a sex-limited, age-related, complex trait. We study MPB genetics in 205,327 European males from the UK Biobank. Here we show that MPB is strongly heritable and polygenic, with pedigree-heritability of 0.62 (SE = 0.03) estimated from close relatives, and SNP-heritability of 0.39 (SE = 0.01) from conventionally-unrelated males. We detect 624 near-independent genome-wide loci, contributing SNP-heritability of 0.25 (SE = 0.01), of which 26 X-chromosome loci explain 11.6%. Autosomal genetic variance is enriched for common variants and regions of lower linkage disequilibrium. We identify plausible genetic correlations between MPB and multiple sex-limited markers of earlier puberty, increased bone mineral density (r <sub>g</sub>  = 0.15) and pancreatic β-cell function (r <sub>g</sub>  = 0.12). Correlations with reproductive traits imply an effect on fitness, consistent with an estimated linear selection gradient of -0.018 per MPB standard deviation. Overall, we provide genetic insights into MPB: a phenotype of interest in its own right, with value as a model sex-limited, complex trait

Numerical analysis of the radio-frequency single-electron transistor operation

We have analyzed numerically the response and noise-limited charge sensitivity of a radio-frequency single-electron transistor (RF-SET) in a non-superconducting state using the orthodox theory. In particular, we have studied the performance dependence on the quality factor Q of the tank circuit for Q both below and above the value corresponding to the impedance matching between the coaxial cable and SET.Comment: 14 page

Simulation Experiments on Efficiencies of Gene Introgression by Backcrossing

Designing a highly efficient backcross (BC) marker-assisted selection (MAS) experiment is not a straightforward exercise, efficiency being defined here as the ratio between the resources that need to be invested at each generation and the number of generations required to achieve the selection. This paper presents results of simulations conducted for different strategies, using the maize genome as a model, to compare allelic introgression with DNA markers through BCs. Simulation results indicate that the selection response in the BC1 could be increased significantly when the selectable population size (N sl) is 100. Selectable population size is defined as the number of individuals with favorable alleles at the target loci from which selection with markers can be carried out on the rest of the genome at nontarget loci, simulations considered the allelic introgression at one to five target loci, with different population sizes, changes in the recombination frequency between target loci and flanking markers, and different numbers of genotypes selected at each generation. For an introgression at one target locus in a partial line conversion, and using MAS at nontarget loci only at one generation, a selection at BC3 would be more efficient than a selection at BC1 or BC2, due to the increase over generations of the ratio of the standard deviation to the mean of the donor genome contribution. With selection only for the presence of a donor allele at one locus in BC1 and BC2, and MAS at BC3, lines with <5% of the donor genome can be obtained with a N sl of 10 in BC1 and BC2, and 100 in BC3 These results are critical in the application of molecular markers to introgress elite alleles as part of plant improvement program

Genetic influences on the difference in variability of height, weight and body mass index between Caucasian and East Asian adolescent twins.

Objective: Twin studies are useful for investigating the causes of trait variation between as well as within a population. The goals of the present study were two-fold: First, we aimed to compare the total phenotypic, genetic and environmental variances of height, weight and BMI between Caucasians and East Asians using twins. Secondly, we intended to estimate the extent to which genetic and environmental factors contribute to differences in variability of height, weight and BMI between Caucasians and East Asians. Design: Height and weight data from 3735 Caucasian and 1584 East Asian twin pairs (age: 13-15 years) from Australia, China, Finland, Japan, the Netherlands, South Korea, Taiwan and the United States were used for analyses. Maximum likelihood twin correlations and variance components model-fitting analyses were conducted to fulfill the goals of the present study. Results: The absolute genetic variances for height, weight and BMI were consistently greater in Caucasians than in East Asians with corresponding differences in total variances for all three body measures. In all 80 to 100% of the differences in total variances of height, weight and BMI between the two population groups were associated with genetic differences. Conclusion: Height, weight and BMI were more variable in Caucasian than in East Asian adolescents. Genetic variances for these three body measures were also larger in Caucasians than in East Asians. Variance components model-fitting analyses indicated that genetic factors contributed to the difference in variability of height, weight and BMI between the two population groups. Association studies for these body measures should take account of our findings of differences in genetic variances between the two population groups. © 2008 Macmillan Publishers Limited All rights reserved.link_to_subscribed_fulltex