Question 1

Which of the following best describes heritability in a population?

Accepted Answer

Heritability is the proportion of the variance in a phenotype within a population that is due to variance in the genotype.

Question 2

A scientist measures the variance in stem length in a population of wheat and finds $$V_T = 12$$ and $$V_E = 3. $$What is the genetic variance $$V_G$$?

Accepted Answer

$$V_G = 9$$

Question 3

Which equation correctly expresses total phenotypic variance?

Accepted Answer

$$V_T = V_G + V_E$$

Question 4

If a trait has a heritability of 0.8 in a population, what does this mean?

Accepted Answer

80% of the variance in the trait within the population is due to genetic differences.

Question 5

Why does heritability apply to populations and not individuals?

Accepted Answer

Because heritability measures the proportion of phenotypic variance due to genetic differences among individuals in a population.

Question 6

In a field of genetically uniform (clonal) corn, you observe variation in yield-per-plant. If you cross the lowest-yield plants with each other, what yield do you expect in the offspring?

Accepted Answer

The same average yield as the previous population

Question 7

Which of the following would increase the heritability of a trait in a population?

Accepted Answer

Increasing genetic variance or decreasing environmental variance

Question 8

A scientist crosses two highly inbred wheat strains that differ in stem height. She self-crosses within the F1 generation and raises the F2. The average $$s^2 of $$the parentals and the F1 = 3, while the $$s^2 of $$the F2 generation = 12. What is the genetic variance of the population?

Accepted Answer

9

Question 9

Which scenario demonstrates that a trait is heritable in a selection experiment?

Accepted Answer

The mean of the trait changes in the offspring when the environment is kept the same.

Question 10

If the same trait has different heritabilities in two populations, what is the most likely explanation?

Accepted Answer

The relative contributions of genetic and environmental variance differ between the populations.

Question 11

Which of the following best estimates the total environmental variance $$V_E$$ given the following variances: $$1.92$$, $$2.05$$, $$2.88$$?

Accepted Answer

$$(1.92 + 2.05 + 2.88)/3$$

Question 12

Which of the following is NOT a correct interpretation of heritability?

Accepted Answer

Heritability tells us how much of a trait is genetically determined in an individual.

Question 13

Which of the following is a correct formula for calculating genetic variance?

Accepted Answer

$$V_G = V_T - V_E$$

Question 14

In a population, the total phenotypic variance $$V_T is 20$$, and the environmental variance $$V_E is 5. $$What is the heritability $$h^2$$?

Accepted Answer

$$h^2$$ = \frac{15}{20}$$

Question 15

Which of the following statements about the gene pool is correct?

Accepted Answer

The gene pool is the total collection of alleles present in all members of a population.

Question 16

If environmental variance is reduced in a population, what happens to heritability?

Accepted Answer

Heritability increases.

Question 17

Which of the following best describes the relationship between genotype frequencies and allele frequencies?

Accepted Answer

Genotype frequencies depend on the allele frequencies in the gene pool.

Question 18

A population of plants is grown in two different environments. The same genotype produces different phenotypes in each environment. What does this illustrate?

Accepted Answer

Environmental variance can affect phenotype even when genotype is constant.

Question 19

In a selection experiment, if the mean of a trait does not change after crossing individuals with extreme phenotypes, what does this suggest?

Accepted Answer

The trait is not heritable; variance is due to environment.

Heritability and Phenotypic Variance in Population Genetics

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