Estimating heritability

The estimation of heritability is based on the resemblance between relatives.

The possibilities for estimation can be based on

• results of selection,
• regression between relatives,
• correlation between relatives,
• Variance between and within relative groups.

Estimation by results of selection

The heritability is

h2 = SE/SD

where

SR = selection response

SD = selection differential

Estimation by using regression

y = a +b x

where

y = progeny performance,

x = parental performance

b = regression

a = constant

When performances of both parents are known then x is the mean of the sire’s and dam’s performance

h2 = b

When the performance of only one parent is known then

h2 = 2b

Estimation by correlation

• Correlation of full-sibs and half-sibs can be used. Also square of correlation between genetic value
• (Breeding value) and phenotypic value is heritability.

Estimation by ANOVA

When having to compute genetic and phenotypic variance for computing h2.

As it was discussed in previous parts, VP = VG + VE. Heritability is the ratio of genetic (VG) and

phenotypic (VP) variance

h2 = VG /(VG +VE)

Performances of paternal half-sib groups are very often used for estimation. In this case, the phenotypic variance between, or among progeny groups is considered genetic variance (VG, or σ2g), while the phenotypic variance within progeny groups is considered environmental variance (VE, or σ2E).

The sum of these gives phenotypic variance (VP = VG + VE, vagy σ2P = σ2G + σ2E).

then

h2 = 4VG/VP = 4VG/(VG + VK,)

vagy

h2 = 4σ2g/σ2p = 4σ2g/σ2g + σ2k