Heritability is a function of a population

• As heritability is a function of both the genetic and environmental variance, it is strictly a property of a population.
• Different populations, even if closely related, can have very different heritability.
• Since heritability is a measure of the standing genetic variation zero heritability does not mean that a trait is not genetically determined.
• For example, an inbred line may show consistent features that are the result of genetic differences relative to other lines. However, since there is no variation within this hypothetical inbred population, h2 is zero.
• As the universe of environment changes, when significant G x E is present, this can change the genotypic values, and hence any appropriate genetic variance.
• As mentioned h2 is the proportion of total variance attributable to differences in breeding values.
• Further, h2 is the slope of regression predicting breeding value given an individual’s phenotypic value, as

A = σ(P, A)/σ2P(P – μP) + e = h2(P – μP) + e

Where,

A = Breeding Value

P = Phenotypic value

σ2P.= Phenotypic variance

μP= Phenotypic regression

e = Error

• The larger the heritability, the higher the distribution of true breeding values around the value h2(P – μP) predicted by an individual’s phenotype.