Heritability in population genetics
Heritability in the narrow sense

Heritability in the narrow sense $h_N$ is the genetic variance $V_G$ over the overall phenotypic variance $V_P$

$$h_N = \frac{V_G}{V_P}$$

More information at Why is a heritability coefficient not an index of how “genetic” something is?.

Heritability in the broad sense

The heritability in the broad sense $h_B$ is the additive genetic variance $V_A$ over the overall phenotypic variance $V_P$

$$h_B = \frac{V_A}{V_P}$$

Decomposing of the genetic variance

Adding together the additive genetic variance $V_A$, the dominance genetic variance $V_D$ (and the epistatic genetic variance $V_I$) sums up to the overall genetic variance $V_G$. Here I will ignore the epistatic genetic variance

$$V_G = V_A + V_D$$

, where

$$V_D = x^2(1-x)^2(2\cdot M_{12} - M_{11} - M_{22})^2$$

$$V_A = 2x(1-x)(xM_{11}+(1-2x)M_{12} - (1-x)M_{22})^2$$

, where $M_{00}$, $M_{01}$ and $M_{11}$ are the measurements of the phenotypic trait in genotypes 00, 01 and 11 respectively.

Highly related


Why is a heritability coefficient not an index of how “genetic” something is?
Additive genetic variance with nn alleles
Additive genetic variance with nn loci