Testing for developmental changes in gene expression on resemblance for quantitative traits in kinships of twins: application to height, weight, and blood pressure.

Height, weight, and blood pressure measurements on identical and fraternal twins and their families were analyzed to assess the degree to which genetic effects may change with age. The blood pressure data were based on the total sample of 1,767 individuals, while height and weight were available on 1,640 individuals in 204 monozygotic twin kinships. The results of testing alternative hypotheses about developmental changes in gene expression indicate that different mechanisms may be operative for these traits. While there was no evidence that developmental effects are a significant source of the observed variation in systolic or diastolic blood pressure, there was strong evidence that genetically determined developmental changes are an important factor in the determination of body weight. Age-related changes in weight appeared to be best explained by the cumulative developmental effects of a single set of genes, rather than by the expression of new genes at different stages of development.