a. Suppose you are interested in selectively breeding livestock to improve vario

Question

a. Suppose you are interested in selectively breeding livestock to improve various characteristics. Which is going to be more important to you, understanding VG or understanding VA? In other words, if you want to have the greatest improvements in the livestock, is it more important to focus on selecting for traits with a high VG or a high VA?

b. Looking over your answer to part “a”, is broad-sense heritability or narrow-sense heritability a better predictor of whether or not a particular trait will respond to selection?

Explanation / Answer

a). Broad-sense heritability is the ratio of genotypic variance to the total phenotypic variance (includes the additive, dominant and epistatic variances).

H2 = Var (G)/ Var (P).

Narrow sense heritability is the phenotypic variation explained by the additive genetic variance (excludes the dominant and epistatic variances).

H2 = Var (A)/ Var (P)

So, it is important to focus on selecting for traits with a high VA (or additive variance).

b). To test the effect of artificial selection on livestock, we should choose narrow sense heritability because it only expresses the genetic variance due to selection.

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