Question

Selection of the parents

• A. reduces additive genetic variance in progeny
• B. increases additive genetic variance in progeny
• C. does not change additive genetic variance in progeny
• D. increases additive genetic variance in sibs

Hint:

The Bulmer effect explains why the response to selection is often highest in the first few generations and then slows down as the additive genetic variance decreases.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Selection is the process of choosing specific animals to parent the next generation.
While selection increases the mean performance of the population, it also alters the genetic structure and variance of the offspring.

Step 2: Detailed Explanation:
The effect of directional selection on genetic variance is described by the Bulmer effect:
Selecting parents based on their phenotypes creates linkage disequilibrium (negative correlations between alleles at different loci that affect the trait).
This linkage disequilibrium reduces the additive genetic variance in the offspring of the selected parents.
This reduction in variance occurs immediately in the first generation of selection, even before gene frequencies change significantly.
When selection is relaxed, these negative correlations are broken down by recombination, and the additive genetic variance largely recovers.
Therefore, selecting parents reduces the additive genetic variance in the progeny generation.

Step 3: Final Answer:
Selection of the parents reduces the additive genetic variance in progeny.