You are studying the effect of directional selection on body height in three pop

Question

You are studying the effect of directional selection on body height in three populations (a, b, and c).

(a) What is the selection differential? Show your calculation.

(b) Which population has the highest narrow sense heritability for height? Explain your answer.

(c) If you examined the offspring in the next generation in each population, which population would have the highest mean height? Why?

Short Mean of population = 65 inches Mean of breading parents 70 inches Short Short Tall Short Mean of population = 65 inches Mean of breading parents 70 inches . Short Short Tall Short Mean of population 65 inches Mean of breading parents 70 inches Short Short Tall Midparent height (average height of mother and father)

Explanation / Answer

A)

Anotheruse of heritability is to determine how a population will respond to selection. Typically parents with a phenotypic value of interest are selected from a base population. These parents are crossed, and a new population is developed.

Selection differential is the difference of the base population mean and the mean of selected parents.

So here mean of breeding parents SP = 70 inches

Mean of population SO = 65 inches

So, let the selection differential be S. Then,

S = SP - SO

S = 70 - 65

S = 5 inches

Hence, selection differential in the above cases is 5 inches.

B)

Height in humans is a classical quantitative trait, easy to measure and studied for well over a century as a model of investigating the genetic basis of complex traits. The heritability of height has been estimated to be ~ 0.8. Rare mutations that cause extreme short or tall stature have been found, but these do not explain much of the variation in the general population.

According to the survey above, A population will have the highest narrow sense heritability for height. This is explained by the graph itself. Parents producing the offsprings will have the short stature height offsprings as the slope of the graph is going to be constant.

C)

C population will have the highest mean height in the coming population. This can be explained by the graph itself. This is so, that the slope is going diagonally above indicating the increase in height of the population.

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