ANSC 322 - Exam 2 What is heritability and why do you need to know article

How does the article formally define “heritability”

Heritability is defined as “the fraction of the variation in phenotype of a trait that is accounted for by the variation in genotype.”

In the context of the article, why is heritability considered a concept from population genetics rather than individual genetics?

Because heritability describes how much of the variation in a trait among a group of individuals is due to genetic differences, not how much of a trait in an individual is determined by gen

Why can a breeder not assume that a trait with a given heritability value means a dog will definitely express that trait?

Because heritability applies to a population’s variation, not to predicting a specific individual’s trait expression. A high heritability doesn’t guarantee the individual will show the trait, just that genes contribute strongly to variation in the population.

What are common misconceptions about heritability that the article highlights?

Two common misconceptions:

• (1) That a heritability of, say, 0.25 means “25% of the trait is determined by genes.” Actually it means 25% of the variation in the trait in the group is due to genetic variation.

• (2) That low heritability means genes don’t matter. In fact, a trait with low heritability still has gene influence—it’s just that environmental variation accounts for more of the population variance.

According to the article, what effect does reducing environmental variation among animals have on heritability estimates?

Reducing environmental variation tends to increase heritability, because less of the trait variation is due to environment, so a greater fraction of remaining variation is due to genes.

Why is understanding heritability important for a breeder selecting dogs for particular traits?

Because if a trait has high heritability, phenotype (what you see) is a better indicator of genotype (what genes are likely present), making selection more efficient. If heritability is low, selecting by phenotype alone is much less reliable.

Can heritability of a trait be considered a fixed value for that trait? Why or why not?

No — heritability is not fixed for a trait because it depends on the specific population and environment. In different populations or environments, heritability can differ.

What does heritability not tell you, according to the article?

It does not tell you:

• Which specific genes are involved.

• How much of a trait in an individual is determined by genes.

• How easily the trait can be changed by environment.

Provide an example scenario used in the article to illustrate when heritability would be very high.

If you have a litter of puppies all raised under identical conditions (same food, exercise, environment), then any differences between them in a trait would be entirely due to genes — so heritability would be very high (close to 1).

For a trait with heritability of 0.30 in a dog population, how should a breeder interpret that number?

It means that 30% of the variation in that trait across the population is explained by genetic differences, and 70% of the variation is due to environmental or other non-genetic factors. It doesn’t mean 30% of each individual’s trait is genetic.