PURPOSE The purpose of this study was to examine the relative influence of genetic and environmental factors on variation in truancy during high school. We examined the significance of genetic and shared and nonshared environmental influences. In addition, we tested for the presence of environmental factors specifically shared by twins, but not by their siblings. METHODS A threshold model was...

There has recently been great interest in applying theoretical quantitative genetic models to empirical studies of evolution in wild populations. However, while classical models assume environmental constancy, most natural populations exist in variable environments. Here, we applied a novel analytical technique to a long-term study of birthweight in wild sheep and examined, for the first time, ...

to determine the yield stability, adaptability and analysis of the genotype× environment interaction of virginia tobacco, 15 hybrids of tobacco including 10 iranian and 5 international hybrids were evaluated in two different experiments (water stress and normal irrigation) using a randomized complete block design (rcbd) with three replications at two locations including rasht and tirtash tobacc...

Heterogeneity of variance of growth traits over age is a common issue in estimating genetic parameters and is addressed in this study by selecting appropriate variance structure models for additive genetic and environmental variances. Modeling and partitioning those variances connected with analyzing small data sets were demonstrated on Lipizzan horses. The following traits were analyzed: withe...

There is evidence in different species of genetic control of environmental variation, independent of scale effects. The statistical power to detect genetic control of environmental or phenotypic variability for a quantitative trait was investigated analytically using a monozygotic (MZ) twin difference design and a design using unrelated individuals. The model assumed multiplicative or additive ...

BACKGROUND/AIMS Well dilated pupils make eye surgery easier. A classic twin study was established to examine the relative importance of genes and environment in the variance of pupil size after mydriasis, and to examine the effects of other factors such as age, iris colour, and refractive error. METHODS 506 twin pairs, 226 monozygotic (MZ) and 280 dizygotic (DZ), aged 49-79 (mean age 62.2 yea...

Letter to the Editor