Deck 25: Quantitative Genetics

Question 1

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

Answer 1

C

Question 2

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 the answers are correct

Answer 2

D

Question 3

Inbreeding reduces which of the following variances to near zero?

A) Genetic variance
B) Environmental variance
C) Both variances
D) Neither variance

Answer 3

A

Question 4

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.

Question 5

The square root of the variance is called the .

A) Mean
B) Standard deviation
C) Standard error
D) Covariance
E) None of the answers are correct

Question 6

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 7

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 the above must be true

Question 8

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 9

The fact that quantitative traits may be based on a polygenic basis was first discovered in studies of
DDT resistance in Drosophila.

Question 10

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

Question 11

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

Question 12

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

Question 13

Quantitative traits usually have which of the following characteristics?

A) Environmental influence
B) Polygenic basis
C) Continuous distribution
D) All of the answers are correct

Question 14

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 15

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 16

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 17

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 the answers are correct

Question 18

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 the answers are correct

Question 19

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 20

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 the answers are correct

Question 21

Realized heritability may be determined from artificial selection experiments.

Question 22

Before conducting a regression analysis, it is first necessary to show that two variables have a cause-
effect relationship using a correlation coefficient calculation.

Question 23

Traits that fall into discrete categories are called continuous traits.

Question 24

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

Question 25

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

Question 26

A regression analysis predicts how much one variable will change in response to a change in a second
variable.

Question 27

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

Question 28

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

Question 29

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

Question 30

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

Question 31

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 32

QTL stands for quantitative trait loci and is an example of monogenic inheritance.

Question 33

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