Heritability is a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population. The concept of heritability can be expressed in the form of the following question: "What is the proportion of the variation in a given trait within a population that is not explained by the environment or random chance?"
Studies of heritability ask questions such as to what extent do genetic factors influence differences in height between people. This is not the same as asking to what extent do genetic factors influence height in any one person.
Figure 3. Twin concordances for seven psychological traits (sample size shown inside bars), with DZ being fraternal and MZ being identical twins.
Figure 4. Strength of selection (S) and response to selection (R) in an artificial selection experiment, h2=R/S.
Quantitative genetics is the study of quantitative traits, which are phenotypes that vary continuously—such as height or mass—as opposed to phenotypes and gene-products that are discretely identifiable—such as eye-colour, or the presence of a particular biochemical.
Gene effects and phenotype values.
Population mean across all values of p, for various d effects.
Genetic drift example analysis.
