How do genetic value and breeding value differ?

How do genetic value and breeding value differ?

• A. The breeding value is the portion transmitted to offspring; the genetic value includes dominance and epistasis that are not transmitted
• B. The breeding value equals the genetic value
• C. The genetic value is always higher than breeding value
• D. The breeding value only accounts for environmental effects

Answer: (C)

The key idea is that a genetic value (genotypic value) represents the total effect of all alleles in an individual on its genotype or phenotype, including additive, dominance, and epistatic interactions. The breeding value is the additive portion of that value—the part that's transmitted to offspring in a predictable way through the additive genetic contributions of the parents. Dominance and epistasis affect the individual's phenotype but aren’t reliably passed on as a simple additive effect to progeny, so they belong to the genetic value but not to the breeding value. Therefore, the breeding value is the portion of the genetic value that can be transmitted to offspring, while the genetic value includes non-additive components as well. It’s not accurate to say the genetic value is always higher than the breeding value—if there are no non-additive effects, they are effectively equal.

The key idea is that a genetic value (genotypic value) represents the total effect of all alleles in an individual on its genotype or phenotype, including additive, dominance, and epistatic interactions. The breeding value is the additive portion of that value—the part that's transmitted to offspring in a predictable way through the additive genetic contributions of the parents.

Dominance and epistasis affect the individual's phenotype but aren’t reliably passed on as a simple additive effect to progeny, so they belong to the genetic value but not to the breeding value. Therefore, the breeding value is the portion of the genetic value that can be transmitted to offspring, while the genetic value includes non-additive components as well.

It’s not accurate to say the genetic value is always higher than the breeding value—if there are no non-additive effects, they are effectively equal.