Q: Which formula is used to calculate the number of contributing alleles from phenotype data?

$$\frac{\text{largest phenotype} - \text{smallest phenotype}}{\text{number of contributing alleles}}$$

Question 1

Which of the following best describes a quantitative trait in genetics?

Accepted Answer

A trait that is influenced by multiple genes and environmental factors, showing continuous variation.

Question 2

A researcher measures the heights of 100 plants and finds the mean height is 50 cm. The sum of squared differences from the mean is 400 cm². What is the variance of the sample?

Accepted Answer

$$s^2$$ = \frac{400}{99}$$

Question 3

Which graph type is most appropriate for displaying the frequency distribution of a quantitative trait such as human height?

Accepted Answer

Histogram

Question 4

In a population, the standard deviation of a trait is 4 units and the sample size is 16. What is the standard error of the mean?

Accepted Answer

$$\frac{4}{\sqrt{16}} = 1$$

Question 5

Which statement about correlation in quantitative genetics is correct?

Accepted Answer

Correlation describes the degree of association between two traits, but does not imply causation.

Question 6

A bell-shaped curve in a histogram of a quantitative trait indicates:

Accepted Answer

The trait follows a normal (Gaussian) distribution.

Question 7

If a trait is influenced by five additive alleles, how many distinct phenotypic categories can be observed?

Accepted Answer

$$2 	imes 5 + 1 = 11$$

Question 8

Which of the following is a threshold trait?

Accepted Answer

Heart disease, which appears only when a certain liability threshold is crossed

Question 9

What does the variance of a trait measure?

Accepted Answer

The degree to which individual measurements differ from the mean.

Question 10

In quantitative genetics, what does the covariance between two traits indicate?

Accepted Answer

The degree of association between the two traits.

Question 11

A population of chickens lays between 2 and 10 eggs per clutch. If the number of contributing alleles is 4, what is the expected number of phenotypic categories?

Accepted Answer

$$2 	imes 4 + 1 = 9$$

Question 12

Which of the following is NOT a component of genetic variation in quantitative traits?

Accepted Answer

Mendelian inheritance of a single gene

Question 13

A scatter plot is most useful for studying:

Accepted Answer

The relationship between two quantitative traits

Question 14

Which formula is used to calculate the number of contributing alleles from phenotype data?

Accepted Answer

$$\frac{	ext{largest phenotype} - 	ext{smallest phenotype}}{	ext{number of contributing alleles}}$$

Question 15

Which of the following best explains why quantitative traits often show continuous variation?

Accepted Answer

They result from the additive effects of multiple genes and environmental factors.

Question 16

If the correlation coefficient ($$r) $$between two traits is 0.9, how would you describe their relationship?

Accepted Answer

Strong association

Question 17

Which of the following is a real-world example of a multifactorial trait?

Accepted Answer

Height in humans

Question 18

What is the main difference between qualitative and quantitative traits?

Accepted Answer

Qualitative traits are controlled by one or few genes, while quantitative traits are controlled by many genes and show continuous variation.

Question 19

Which statistical measure is used to describe the average squared deviation from the mean in a sample?

Accepted Answer

Variance

Question 20

In a study of grain color in wheat, the multiple-gene hypothesis explains the observed variation as:

Accepted Answer

The cumulative effect of several genes, each contributing additively to the phenotype.

Quantitative Genetics and Polygenic Inheritance: Study Notes

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