Deck 27: Quantitative Genetics

Question 1

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

Answer 1

True

Question 2

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

Answer 2

False

Question 3

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

Answer 3

D

Question 4

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

Question 5

What is trure concerning a quantitative trait?

A)Individuals fall into distinct classes for comparison
B)The phenotypic variation for the trait is continuous
C)The phenotypic variation for the trait falls into two to three classes
D)The frequency distribution of the trait will have an asymmetrical shape

Question 6

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 7

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

Question 8

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

Question 9

QTL mapping can rely on 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 10

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

Question 11

Traits that fall into discrete categories are called continuous traits.

Question 12

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

Question 13

The square root of the variance is called the _____.

A)Mean
B)Standard deviation
C)Standard error
D)Covariance

Question 14

Realized heritability may be determined from artificial selection experiments.

Question 15

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

Question 16

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 17

Heterosis is _______.

A)the combination of lethal alleles due to inbreeding
B)an increased vigor of hybrids resulting from the crossing of inbred strains
C)a measurement of the variance due to environmental factors
D)the result of homozygosity of multiple, dominant, detrimental alleles.

Question 18

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 19

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 20

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 21

What is the mean height for the mothers and daughters?

A)Mothers: 66.75 inches Daughters: 67.62 inches
B)Mothers: 65.75 Daughters: 67.62
C)Mothers: 66.75 Daughters: 66.52
D)Mothers: 65.67 Daughters: 66.45

Question 22

The equation that describes the relationship between phenotypic variance, genetic variance and environmental variance is

A)V_P = V_G + V_E
B)1 = V_G + V_E + V_P
C)V_E = V_G + V_P
D)V_G = V_P + V_E

Question 23

What is the standard deviation for the mother's and daughter's heights?

A)Mothers: 6.07 Daughters: 4.6
B)Mothers: 5.07 Daughters: 4.6
C)Mothers: 6.07 Daughters: 5.6
D)Mothers: 4.07 Daughters: 4.6

Question 24

Calculate the narrow-sense heritability of height between aunts and neices if the observed phenotypic correlation coefficient is 0.1.

A)0.4
B)2.5
C)4
D)0.25

Question 25

What is the correlation coefficient between mother and daughter height and would it be considered significant?

A)Correlation coefficcient: 0.49 Not significant
B)Correlation coefficcient: 0.31 Not significant
C)Correlation coefficcient: 0.49 Significant
D)Correlation coefficcient: 0.31 Significant

Question 26

Inbreeding reduces which of the following variances to near zero?

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

Question 27

Polygenic inheritance may result in a continuum of phenotypes because

A) the genes that are involved can be considered to be co-dominant.
B) the alleles for each gene are either completely dominant or recessive.
C) there is a low environmental effect.
D) there is a high environmental effect.

Question 28

To use a backcross mating strategy for QTL mapping

A)two inbred parental strains that differ in a quantitative trait are crossed are mated.
B)the F₁ offspring are crossed with each other.
C)the F₂ offspring must contain chromosomes that are recombinant betweeen the markers and the genes involved in the trait
D)each parent should contain the same alleles at each QTL.

Question 29

What is the variance for the mother's and daughter's heights?

A)Mothers: 42.21 Daughters: 24.26
B)Mothers: 41.32 Daughters: 23.71
C)Mothers: 43.78 Daughters: 24.26
D)Mothers: 42.21 Daughters 23.78

Question 30

What is a typical characteristic of a quantitative trait?

A) No environmental influence on the trait
B) Polygenic basis
C) Discontinuous distribution of phenotypic trait.
D) Usually the graph of trait versus frequency has two distinct peaks.

Question 31

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

Question 32

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 33

Eye color in Drosophila is an example of

A) Discontinuous, non-quantitative trait
B) Discontinuous, quantitative trait
C) Continuous, non-quantitative trait
D) Continuous, quantitative trait

Question 34

The best definition for genotype-environment interactions is

A)Environmental effects on the phenotype differ with genotype.
B)Environment does not affect phenotype.
C)Phenotypes will always be affected by the environment no matter what the genotype
D)Genotypes and phenotypes do not change with environmental conditions

Question 35

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

Question 36

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

Question 37

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

Question 38

Since quantitative traits can be described by a plot of the frequency vs value of the trait since

A)the trait can have a range of values.
B)the traits are discrete.
C)the traits are discontinuous
D)the traits are frequently the result of a single gene with more than two alleles.

Question 39

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

Question 40

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 41

A selective breeding program is trying to develop an agircultural plant with decreased stem length to aid in mechanical harvesting. The mean stem height of the popluation is 36 cm while the mean stem height of the parents is 30 cm and the mean stem height of the offspring is 33 cm. What is the realized heritability for stem height in this crop?

A) 1
B) 3
C) -3
D) 0.1

Question 42

In an experiment two inbred strains are mated to each other and the offspring demonstrate heterosis. The offspring (F₁'s) are crossed to each other and a ratio is obtained where there are 9 individuals that demonstrate heterosis and 7 that are similar to the original parental generation. What is this most likely a demonstration of?

A)Dominance hypothesis
B)Overdominance hypothesis
C)Cannot tell from the information given.
D)That there is a significant environmental interaction in phenotypic development