Explain the difference between broadsense and narrowsense he

Explain the difference between broad-sense and narrow-sense heritability? Which is the more relevant measure if you are trying to predict how livestock will respond to artificial selection to improve a trait? Why?

Solution

Heritability is defined as ratio of Genetic variance to Total variance. This can be of two types-

1. Broad sense heritability: Here we consider total genetic variance. Now genetic variance comprises of three factors or we can say is influenced by three factors i.e. additive genes, dominance and epistasis. Each of these have a separate component, and we describe them like this-

V_G = V_A + V_D+ V_I, respectively.

The formula for Heritability would be-

H² = V_G / V_P

where Vp is the total variance.

2. Narrow sense heritability : Here we consider only the additive genetic variance component. It means we are considering what is the contribution of individual allele on the phenotype of the offspring.

h² = V_A / Vp.

In our experiment, since we are considering artificial selection, that means we are eliminating the \"Environmental\" aspect or influence on the phenotype. Thus, narrow sense heritability is more relevant to measure the outcome. This is because we would go for more better output giving alleles. Therefore, considering additive variance component more as compared to epistatic or environmental variance.