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Estimating Heritability from Nuclear Family and Pedigree Data

Protocol
First Online:
Part of the Methods in Molecular Biology book series (MIMB, volume 850)

Abstract

Heritability is a measure of familial resemblance. Estimating the heritability of a trait represents one of the first steps in the gene mapping process. This chapter describes how to estimate heritability for quantitative traits from nuclear and pedigree data using the ASSOC program in the Statistical Analysis for Genetic Epidemiology (S.A.G.E.) software package. Estimating heritability rests on the assumption that the total phenotypic variance of a quantitative trait can be partitioned into independent genetic and environmental components. In turn, the genetic variance can be divided into an additive (polygenic) genetic variance, a dominance variance (nonlinear interaction effects between alleles at the same locus), and an epistatic variance (interaction effects between alleles at different loci). The last two are often assumed to be zero. The additive genetic variance represents the average effects of individual alleles on the phenotype and reflects transmissible resemblance between relatives. Heritability in the narrow sense (h 2) refers to the ratio of the additive genetic variance to the total phenotypic variance. Heritability is a dimensionless population-specific parameter. ASSOC estimates association parameters (regression coefficients) and variance components from family data. ASSOC uses a linear regression model in which the total residual variance is partitioned, after regressing on covariates, into the sum of a random additive polygenic component, a random sibship component, random nuclear family components, a random marital component, and an individual-specific random component. Assortative mating, nonrandom ascertainment of families and failure to account for key confounding factors may bias heritability estimates.

Key words

Heritability Additive genetic variance Polygenic variance Total phenotypic variance Narrow sense heritability Broad sense heritability Familial aggregation Variance components Environmental variance Genetic variance Pedigrees Family data Nuclear families 
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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  1. 1.Institute of Social and Preventive MedicineUniversity of LausanneLausanneSwitzerland

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