Question 1

Which of the following best describes a quantitative (continuous) characteristic in genetics?

Accepted Answer

A trait influenced by multiple genes with additive effects, resulting in a wide range of phenotypes, such as human height.

Question 2

In the Nilsson-Ehle experiment on wheat kernel color, what is the expected phenotypic ratio in the F2 generation when two loci are involved, each with two alleles showing additive effects?

Accepted Answer

$$1:4:6:4:1$$

Question 3

A population of fish has a phenotypic variance ($$V_P) of$$ $$0.563\ \mathrm{mm}^2$$ for eye diameter. The variance in a genetically uniform population is $$0.057\ \mathrm{mm}^2. $$What is the genetic variance ($$V_G$$)?

Accepted Answer

$$V_G = 0.506\ \mathrm{mm}^2$$

Question 4

Which equation correctly represents broad-sense heritability ($$H^2$$)?

Accepted Answer

$$H^2$$ = \frac{V_G}{V_P}$$

Question 5

If the mean corolla tube length in the original tobacco population is $$70\ \mathrm{mm}$$, the mean of selected parents is $$81\ \mathrm{mm}$$, and the mean of their F1 offspring is $$77\ \mathrm{mm}$$, what is the narrow-sense heritability ($$h^2$$)?

Accepted Answer

$$h^2$$ = \frac{7}{11} = 0.64$$

Question 6

Which of the following statements about polygenic inheritance is correct?

Accepted Answer

Multiple genes with small, additive effects contribute to the phenotype.

Question 7

A researcher wants to estimate the number of polygenes controlling a trait. If the proportion of F2 individuals showing the extreme phenotype is $$1/64$$, how many loci are likely involved?

Accepted Answer

$$n = 3$$

Question 8

Which of the following best describes a threshold characteristic?

Accepted Answer

A trait that is expressed only when a certain level of genetic and environmental factors is reached.

Question 9

Which component of phenotypic variance ($$V_P) is $$estimated by measuring variance in a genetically uniform population?

Accepted Answer

Environmental variance ($$V_E)$$

Question 10

Which of the following is true regarding the predictive power of additive genetic effects?

Accepted Answer

Additive effects allow accurate prediction of offspring mean phenotype from parental mean.

Question 11

A breeder selects plants with the highest yield from a population. The mean yield of the original population is $$50\ \mathrm{g}$$, the selected group is $$60\ \mathrm{g}$$, and the F1 offspring mean is $$55\ \mathrm{g}. $$What is the selection differential ($$s$$)?

Accepted Answer

$$s = 10\ \mathrm{g}$$

Question 12

Which of the following is NOT a component of broad-sense heritability ($$H^2$$)?

Accepted Answer

Environmental variance

Question 13

Which statistical measure describes the spread of phenotypic values in a population?

Accepted Answer

Variance

Question 14

In a population, the mean value of a quantitative trait in F1 hybrids is intermediate between the two parental means. What does this suggest about the inheritance of the trait?

Accepted Answer

The trait is influenced by multiple genes with additive effects.

Question 15

Which of the following best describes a Quantitative Trait Locus (QTL)?

Accepted Answer

A DNA region associated with variation in a quantitative trait.

Question 16

If the broad-sense heritability ($$H^2) of a $$trait is $$0.9$$, what does this imply?

Accepted Answer

Most of the phenotypic variance is due to genetic differences.

Question 17

Which formula is used to calculate the sample mean ($$\bar{x}) of a $$quantitative trait?

Accepted Answer

$$\bar{x} = \frac{\sum x_i}{n}$$

Question 18

Which of the following is a real-world example of a meristic characteristic?

Accepted Answer

Number of eggs laid by a chicken

Question 19

Which of the following is a correct interpretation of the breeder’s equation $$R = h^2$ 	imes s$$?

Accepted Answer

The response to selection ($$R) is $$the product of narrow-sense heritability ($$h^2) $$and the selection differential ($$s).$$

Quantitative Genetics: Polygenic Inheritance, Statistical Analysis, and Heritability

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