Deck 24: Quantitative Genetics

Question 1

In QTL mapping,the parental strains are crossed and the F₁ generation backcrossed to which of the following?

A) the F₂ generation
B) the parental generation
C) a strain that is homozygous recessive for all markers
D) a wild-type organism

Answer 1

B

Question 2

Which of the following steps is NOT used in conducting a backcross in order to map a QTL?

A) Two inbred strains that differ in a quantitative trait are crossed.
B) The F1 offspring are crossed with each other.
C) The F2 offspring contain different combinations of the parental chromosomes.
D) By using genetic markers, it is determined which parent each chromosome came from and thus isolate the genes.

Answer 2

B

Question 3

Heritability is the amount of genetic variation in a particular population and a particular environment.

Answer 3

True

Question 4

A trait that varies measurably in a species is called a discontinuous trait.

Question 5

Which of the following is incorrect concerning quantitative traits?

A) Individuals fall into distinct classes for comparison.
B) The phenotypic variation for the trait is continuous.
C) The frequency distribution follows a bell-shaped curve.
D) All of these choices are correct.

Question 6

Heritability may be calculated as which of the following?

A) the total variance minus environmental variance
B) total variance minus genetic variance
C) genetic variance divided by environmental variance
D) genetic variance divided by total variance
E) None of these choices are correct.

Question 7

What must be true for a correlation coefficient to be calculated between two traits?

A) The values for the traits must have been obtained from unbiased sampling.
B) The relationship between the two traits must be linear.
C) The traits must follow a normal distribution.
D) All of these choices are correct.

Question 8

A heritability value of 0.997 indicates which of the following?

A) The majority of the phenotypic variation has a genetic basis.
B) The majority of the phenotypic variation has an environmental basis.
C) The trait is polygenic.
D) There is a significant difference between the two strains.
E) None of these choices are correct.

Question 9

The square root of the variance is called the ________.

A) mean
B) standard deviation
C) standard error
D) covariance
E) None of these choices are correct.

Question 10

For a quantitative trait,the total variance of the population is due to which of the following?

A) The amount of variance due to genetic factors only
B) The amount of variance due to environmental factors only
C) The difference between the variance attributed to genetic and environmental factors
D) The sum of the genetic and environmental variances

Question 11

In calculations of the degrees of freedom for a correlation coefficient,what value does the degrees of freedom take?

A) (n - 1)
B) (n - 2)
C) (n - 1)/2
D) 2(n - 1)

Question 12

After calculating a correlation coefficient,you discover that the value is not significant at the 5% level.What can be done to produce a significant difference?

A) increase the sample size
B) decrease the sample size
C) Nothing, the value will remain the same regardless of sample size.

Question 13

Quantitative traits usually have which of the following characteristics?

A) environmental influence
B) polygenic basis
C) continuous distribution
D) All of these choices are correct.

Question 14

What must be true regarding the strains of organisms used to construct a QTL map?

A) they must differ for the quantitative trait
B) they must differ for the molecular markers
C) Both of these choices must be true.

Question 15

When analyzing two variables,the strength of the association between the variables is called the ________.

A) covariance
B) standard deviation
C) correlation coefficient
D) variance

Question 16

Which of the following best describes the degrees of freedom for the calculation of variance?

A) (n + 1)
B) 2(n + 1)
C) (n - 1)/n
D) (n - 1)

Question 17

Heritability values can be compared between populations if there is variation in the environmental conditions.

Question 18

QTL mapping determines the relationship between genes for quantitative traits and which of the following?

A) the centromere
B) transposon sites
C) structural genes
D) molecular markers such as RFLPs

Question 19

After several generations of artificial selective breeding,a plateau is reached where artificial selection is no longer effective. This is called the ________.

A) realized limit
B) realized heritability
C) selection coefficient
D) selection limit

Question 20

Inbreeding reduces which of the following variances to near zero?

A) genetic variance
B) environmental variance
C) both variances
D) neither variance

Question 21

If a completely inbred population shows phenotypic variance,then that variance is caused by environmental  effects.

Question 22

QTL stands for quantitative trait locus and may contain more than one gene.

Question 23

The amount of phenotypic variation in a group that is due to genetic variation is called heritability.

Question 24

The process of mating between genetically unrelated individuals is called inbreeding.

Question 25

Many organisms used in modern agriculture are a result of artificial selection.

Question 26

The variance is the sum of the standard deviation from the mean divided by the degrees of freedom.

Question 27

If the difference between the mean of the parents and the mean of the starting population is 1.0 and the the difference between the mean of the offspring and the mean of the starting population is 0.45 then the realized heritability is

A) 1.45
B) 2.22
C) 0.45
D) 0.55

Question 28

Since quantitative traits are frequently associated with a number of genes and the environment,it is difficult to assign accurate phenotypic classes for a Punnett square diagram.

Question 29

The sum of all of the values for a trait,divided by the total number of individuals,is called the standard deviation.

Question 30

Realized heritability may be determined from artificial selection experiments.

Question 31

A population that is homozygous for a given allele is called monomorphic.

Question 32

Traits that fall into discrete categories are called continuous traits.

Question 33

How do quantitative traits arise? (Check all that apply.)

A) The trait is controlled only be a single gene and there is no environmental effect on the trait.
B) The trait is polygenic.
C) The trait is controlled by a single gene and the environment.
D) The population is inbred with no environmental effect on the trait.