Deck 28: Complex and Quantitative Traits

Question 1

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.

Answer 1

True

Question 2

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

Answer 2

D

Question 3

The first step in the backcross mating strategy for QTL mapping is that

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

Answer 3

A

Question 4

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 5

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

Question 6

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 7

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 8

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 9

Traits that fall into discrete categories are called continuous traits.

Question 10

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 11

Inbreeding reduces which of the following variances to near zero?

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

Question 12

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

Question 13

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

Question 14

What is true 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 15

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 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 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 18

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 19

The square root of the variance is called the ________.

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

Question 20

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 21

Polygenic inheritance may result in a continuum of phenotypes because

A) as the number of genes controlling a trait increases and the influence of environment variation becomes greater, there is a blurring of discreteness
B) the alleles for each gene are either completely dominant or recessive
C) additive genes mean the characters are meristic
D) correlations among various traits are always positive

Question 22

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 23

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

Question 24

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

Question 25

Hybrids resulting from matings of inbred strains often show heterosis, explained by two different hypotheses, overdominance and dominance. What are the predictions of these hypotheses?

A) The Overdominance hypothesis relies on dominant/recessive alleles
B) The Dominance hypothesis relies on the fact that in the F1s, the deleterious effects of recessive alleles are masked by dominant ones

Question 26

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 27

It is possible for a genetically homozygous plant population to show a bell shaped height distribution because

A) of environmental factors.
B) the trait is discrete.
C) there is no genetic variation, all plants will be the same height

Question 28

A selective breeding program is trying to develop an agricultural plant with decreased stem length to aid in mechanical harvesting. The mean stem height of the population 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 29

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

A) VP = VG + VE
B) 1 = VG + VE + VP
C) VE = VG + VP
D) VG = VP + VE

Question 30

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

Question 31

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 32

Realized heritability may be determined from artificial selection experiments.

Question 33

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

Question 34

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

Question 35

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

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

Question 36

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 37

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 38

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 39

If a population has no polymorphisms, then its genetic variance is 0.