Q: Which equation correctly represents the total phenotypic variance ($$V_P) in a $$population?

$$V_P = V_G + V_E + V_{G \times E}$$

Question 1

Which of the following best describes a threshold trait, as illustrated by the development of clinical diabetes in the provided graph?

Accepted Answer

A polygenic trait where the phenotype is expressed only when a certain number of predisposing alleles is exceeded.

Question 2

In the context of polygenic inheritance, what does the term 'additive allele' mean?

Accepted Answer

An allele that contributes equally and cumulatively to the phenotype.

Question 3

A cross between two inbred strains of skunks with stripe lengths of 20 cm and 24 cm produces F1 offspring with 22 cm stripes. The F2 generation shows seven distinct stripe lengths. How many gene pairs are likely involved in determining stripe length?

Accepted Answer

$$n = 3$$

Question 4

If 1/64 of the F2 individuals in a cross show the extreme parental phenotype, how many polygenes are involved in the trait?

Accepted Answer

$$n = 3$$

Question 5

Which equation correctly represents the total phenotypic variance ($$V_P) in a $$population?

Accepted Answer

$$V_P = V_G + V_E + V_{G 	imes E}$$

Question 6

What does a broad-sense heritability ($$H^2) $$value of 0.8 indicate about a trait in a population?

Accepted Answer

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

Question 7

Which formula is used to calculate the number of distinct phenotypic classes in the F2 generation for a polygenic trait?

Accepted Answer

$$(2n+1)$$

Question 8

In a wheat cross, the F2 generation shows a 1:4:6:4:1 ratio for grain color. How many genes are involved in this trait?

Accepted Answer

$$n = 2$$

Question 9

Which of the following best explains why heritability estimates are context-specific and not fixed?

Accepted Answer

Heritability depends on the specific population and environment studied.

Question 10

A researcher finds that the variance in height among inbred lines of plants grown in the same environment is much greater than the variance within each line. What does this suggest?

Accepted Answer

Genetic factors are the main source of variation.

Question 11

Which of the following is true about additive alleles in polygenic inheritance?

Accepted Answer

They contribute equally and cumulatively to the phenotype.

Question 12

If a quantitative trait shows 9 distinct phenotypic classes in the F2 generation, how many polygenes are likely involved?

Accepted Answer

$$n = 4$$

Question 13

Which of the following best describes a multifactorial trait?

Accepted Answer

A trait influenced by multiple genes and environmental factors.

Question 14

What is the formula for narrow-sense heritability ($$h^2$$)?

Accepted Answer

$$h^2 = V_A / V_P$

Question 15

Which of the following is an example of a meristic trait?

Accepted Answer

Number of bristles in Drosophila

Question 16

A population of plants shows a total phenotypic variance ($$V_P) of 100$$, with a genotypic variance ($$V_G) of 60. $$What is the broad-sense heritability ($$H^2$$)?

Accepted Answer

$$H^2 = 0.6$

Question 17

Which of the following statements about threshold traits is correct?

Accepted Answer

They are polygenic traits that are expressed only when a certain threshold is exceeded.

Question 18

In the context of the skunk stripe length problem, what is the contribution of each additive allele if the parental stripe lengths are 20 cm and 24 cm, and the F1 is 22 cm?

Accepted Answer

Each additive allele contributes 1 cm to stripe length.

Question 19

Which of the following best describes the difference between continuous and discontinuous variation?

Accepted Answer

Continuous variation results in a smooth range of phenotypes, while discontinuous variation results in discrete categories.

Polygenic (Quantitative) Inheritance and Heritability

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