Deck 19: The Inheritance of Complex Traits

Question 1

Two pure lines of plants had mean heights of 26 cm and 42 cm,respectively.The F₁ had a mean of 34 cm and a variance of 20.The F₂ also had a mean of 34 but a variance of 60.The broad-sense heritability (H²)is:

A)0.13.
B)0.34.
C)0.50.
D)0.67.
E)0.80 .

Answer 1

0.67.

Question 2

Two different pure-breeding lines of tobacco were crossed and their F₁ showed a variance in flower length of 8.76.The total variance in flower length in the F₂ was 40.96.The F₁ and the F₂ plants were bred,grown,and kept in identical environments.

a)What is the broad-sense heritability of flower length in tobacco in this experiment?

A)8.76%
B)21.38%
C)32.20%
D)78.61%
E)The broad-sense heritability cannot be calculated based on these data.

Answer 2

78.61%

Question 3

When all of the variation in a population is due to environmental sources and there is no genetic variation,broad sense heritability (H²):

A)is zero and all of the phenotypic variability is due to loci at other locations.
B)is zero and all of the phenotypic variability is due to environment.
C)is some negative value indicating the phenotypic variability is due to some recessive loci.
D)is some positive value indicating the phenotypic variability is due to some dominant loci.

Answer 3

B

Question 4

Presume that the number of leaves in clovers is controlled by the combined actions of two genes,A and B,with no contributions from the environment.A/A results in four leaves,A/a in three leaves,and a/a in two leaves.Moreover,the genotypes B/B and B/b result in one additional leaf (b/b has no effect on leaf number). a)Based on the above information:

A)A has an additive mode of action and B has a dominant mode of action.
B)A has a dominant mode of action and B has an additive mode of action.
C)both A and B have a dominant mode of action.
D)both A and B have an additive mode of action.
E)the respective modes of action of A and B cannot be determined.

Question 5

The mean weight in a population of fruit flies (Drosophila melanogaster)grown in identical conditions is 1.10 mg,and the standard deviation is 0.05.The heaviest fly in this population weighs 1.30 mg.The genetic deviation of this individual is:

A)0.05 mg.
B)0.15 mg.
C)0.20 mg.
D)0.84 mg.
E)It is impossible to determine based on these data.

Question 6

Ten pairs of monozygotic twins were tested for their ability to solve geometry problems.The highest score obtained was 46 points,while the lowest was 6 points.The variance in geometry test score within the twenty subjects (measured in points²)was 208.The covariance for test score between twins was 125.In this study,the broad-sense heritability of geometry problem-solving ability is:

A)26%.
B)32%.
C)40%.
D)60%.
E)It is impossible to calculate.

Question 7

The amount of milk produced per day by a cow is an example of a:

A)continuous trait.
B)discrete trait.
C)dominant trait.
D)meristic trait.
E)threshold trait.

Question 8

You are studying a highly inbred strain of barley.After many generations of inbreeding,you now assume that the genetic variation is zero.Suppose that you raise many individuals of your barley strain in a field in southeastern Michigan and then measure their height after one month of growth.You find that the variance in their height is 4.0.The broad-sense heritability of this trait is 0.From this particular study you can conclude that:

A)genetics does not play a major role in determining the height of barley plants.
B)if you were to repeat the same experiment in Iowa,you would obtain a different broad-sense heritability.
C)if you were to repeat the same experiment in Iowa,you would obtain the same broad-sense heritability.
D)in barley plants,height is not inheritable.
E)the line of barley plants that you are studying is not inbred enough.

Question 9

Loppins (fictitious diploid invertebrates)have variable numbers of dots on their abdomen.This variability is entirely due to genetics,with no influence of the environment,so the broad-sense heritability for this trait is 1.The mean number of dots per individual in a large population is 37.A breeder crosses the two animals with the highest number of dots,45.In the progeny,the mean number of dots is 43.4.These results suggest that the phenotype of interest is controlled:

A)at least partly by genes that have an additive mode of action.
B)at least partly by genes that have a dominant mode of action.
C)by genes that have both an additive and a dominant mode of action.
D)only by genes that have an additive mode of action.
E)only by genes that have a dominant mode of action.

Question 10

Narrow-sense heritability (h²)is a quantification of the proportion of total variance due to:

A)additive genetic variance.
B)dominance variance.
C)environmental variance.
D)phenotypic variance.
E)total genetic variance.

Question 11

A large number of genetically identical tomato plants are grown in a greenhouse.The mean height in this plant population is 84 cm,and the standard deviation is 2.5 cm.The variation in height within this population is most likely due to:

A)a correlation between genotype and environment.
B)the difference between the greenhouse population mean and the whole population mean.
C)differences in the plants' microenvironment.
D)random genetic differences within the population.
E)the use of a nonrepresentative sample to compute the mean.

Question 12

Three populations of true-breeding C.elegans larvae are each split into four subpopulations of equal sizes,and each subpopulation is grown in a different environment.The mean adult body lengths in each environment are as follows:

Based on these data,what environment has the highest environmental deviation?

A)both Environments 3 and 4
B)Environment 1
C)Environment 2
D)Environment 3
E)Environment 4

Question 13

A quantitative geneticist measures the broad-sense heritability for bill length in an isolated population of ducks to be 0.75.This result suggests that:

A)the population tested has a high variance in bill length.
B)in the population tested,75% of the variance in bill length is due to genetic differences among individuals.
C)in the population tested,75% of the variance in bill length is due to environmental differences among the individuals' microhabitats.
D)if all the ducks in the population tested were raised in identical environments,75% of them would have identical bill length.
E)in the population tested,75% of the ducks have a bill length that is within one standard deviation of the mean.

Question 14

It is difficult to measure any type of heritability without the ability to perform specific crosses.However,vast population studies enable estimation of heritability for some characters in human beings.Some estimated broad-sense heritabilities include: $$\begin{array} { l l } \text { Character } & H ^ { 2 } \\\hline \text { stature } & 0.85 \\\text { body weight } & 0.62 \\\text { systolic blood pressure } & 0.57 \\\text { diastolic blood pressure } & 0.44 \\\text { twinning } & 0.50\end{array}$$
Which of these characteristics is most likely to "run in families"?

A)body weight
B)diastolic blood pressure
C)stature
D)systolic blood pressure
E)twinning

Question 15

A behavioral biologist suspects the "N" locus to be involved in the learning ability of dogs.Learning is measured through a standardized test in which each dog can score from 0 (very poor)to 20 points (excellent).In an experiment,the mean score was 15.6 for dogs of genotype N/N,12.1 for dogs of genotype N/n and 7.2 for those of genotype n/n.What is the dominance/additivity ratio for this locus?

A)0
B)higher than 0,but lower than 0.5
C)0.5
D)higher than 0.5,but lower than 1
E)1

Question 16

Consider a diploid fish in which tail length is solely controlled by the additive action of two unlinked loci,F (f)and G (g),without any effect of the environment.A female of genotype F/F;G/G,with a 3 cm long tail,is crossed to a male of genotype f/f;g/g,with a 2 cm long tail.All the F₁ fish have 2.5 cm long tails. a)If the F₁ fish are crossed to each other,how many different tail length phenotypes will be present in F₂?

A)16
B)5
C)4
D)3
E)2

Question 17

Suppose that gene A controls the synthesis of blue pigment in the petals of a flowering plant.Plants with genotype A/A produce blue pigment in their petals,while those with genotype A/a or a/a do not produce any blue pigment.The expected narrow-sense heritability (h²)for the production of blue pigment in this plant's flowers is:

A)exactly 0.
B)exactly 0.5.
C)higher than 0,but lower than 1.
D)exactly 1.
E)dependent on the environmental variance.

Question 18

Which of the following statements is/are a central assumption of the multifactorial inheritance hypothesis?

A)Only one locus is associated with the trait.
B)Several loci are associated with the trait.
C)Environment plays no role in the final phenotype.
D)Only one locus is associated with the trait,and environment interacts with this locus to produce the final phenotype.
E)None of the answer options are correct.

Question 19

A high variance indicates that:

A)the mean value is very high.
B)most values are very close to the mean.
C)most values are higher than the mean.
D)most values are lower than the mean.
E)the variation among the values is high.

Question 20

The variance in tail length in a large population of genetically diverse mice is found to be 21.30.The broad-sense heritability for this trait in an identical population was found to be 0.8.Based on this information,what is the predicted genetic variance (V_g)for these mice?

A)4.26
B)17.04
C)20.50
D)21.30
E)26.62

Question 21

Two pure lines of Nicotianum (tobacco)have significantly different corolla lengths.In line 1,the average length is 30 mm,ranging from 25 mm to 35 mm with a variance of 10.In line 2,the average corolla length is 60 mm,ranging from 45 mm to 65 mm with a variance of 12.The F₁ has a corolla length of 45 mm,ranging from 40 to 50,and the variance is 9.Upon selfing,an F₂ is produced that has an average flower length of 45 mm,but ranges from 10 mm to 80 mm with a variance of 55.
a)Provide a general explanation of these results.
b)Calculate the broad-sense heritability (H²)for corolla length in this study.

Question 22

You are studying the inheritance of antennae length in loppins using strains from British Columbia (BC)and Washington State (WA).BC loppins have,on average,much longer antennae than their WA counterparts.You have identified three QTLs that control this trait,and you obtained the following data.

Which QTL(s)has/have the highest dominance effect?

A)QTL1
B)QTL2
C)QTL3
D)QTLs 1 and 2
E)QTLs 1 and 3

Question 23

In a large flock of turkeys,average body weight is 5.0 kg.In a test to determine if the average weight of the flock can be increased by selective breeding,6.2 kg birds are removed and allowed to interbreed.Their progeny have an average weight of 5.2 kg.Calculate the narrow-sense heritability (h²).

Question 24

Imagine that an association mapping study revealed a particular variant of a SNP to be strongly associated with susceptibility to insomnia.From these data,you could infer that:

A)the SNP is closely linked to a locus that plays a role in insomnia.
B)the SNP is located in a gene that determines insomnia.
C)the SNP provides evidence that insomnia is a genetic condition.
D)the variant SNP most likely causes insomnia.
E)the variant SNP plays a role in insomnia.

Question 25

A population of beetles has a mean weight of 30 g.In a controlled,constant environment,individuals of 12 g are selected and allowed to interbreed,and their progeny have a mean weight of 21 g with a variance of 4.5 g².What is the additive variance in this experiment?

A)0.50
B)0.57
C)0.70
D)1.75
E)2.25

Question 26

Three inbred lines of potatoes are cultured in three different environments.The mean tuber weight for each line in each environment is reported below.
$\begin{array} { l l l l } & \text { Line A } & \text { Line B } & \text { Line C } \\\text { Environment 1: } & 131 \mathrm {~g} & 93 \mathrm {~g} & 160 \mathrm {~g} \\\text { Environment 2: } & 180 \mathrm {~g} & 142 \mathrm {~g} & 209 \mathrm {~g} \\\text { Environment 3: } & 97 \mathrm {~g} & 59 \mathrm {~g} & 126 \mathrm {~g}\end{array}$
a)What are the genetic deviations (g)for each of the three lines?
b)What are the environmental effect (e)on tuber weight for each of the three environments?

Question 27

In an experiment carried out in a chicken population,measurements of fat content reveal that the genetic variance for this trait is 120 g²,the environmental variance is 80 g² and the variance due to dominance is 38 g².The narrow-sense heritability (h²)of fat content in these chickens is:

A)0.24.
B)0.41.
C)0.52.
D)0.74.
E)0.90 .

Question 28

a)What is the role of marker genes for the identification of quantitative trait loci?
b)How do they differ from candidate genes?

Question 29

In a population of beetles,the total variance of body weight is 130.It is estimated that the environmental variance is 35,and dominance genetic variance is 45.Calculate the narrow-sense heritability (h²)of body weight in these beetles.

Question 30

Which of the following has more important value to the plant or animal breeder?

A)broad-sense heritability
B)variance
C)correlation
D)additive deviation
E)dominance deviation

Question 31

In a natural population of outbreeding annual plants,the variance of the total number of seeds per plant is 16.From the natural population,20 plants are taken into the laboratory and each selfed for 10 generations.The average variance in the tenth generation in each of the 20 sets is about equal,and averages 5.8 across all the sets.Estimate the broad-sense heritability (H²)of seed number in this population.

Question 32

The phenotypic deviation that is transmitted from parents to their offspring is known as:

A)additive genetic variance.
B)dominance variance.
C)environmental variance.
D)total genetic variance.
E)transmissible variance.

Question 33

The narrow-sense heritability (h²)for several traits in domesticated cattle follow:
$$\begin{array} { l l l } \text { Trait } &{ h ^ { 2 } } \\\hline \text { Percent protein in milk } & 0.54 & \\\text { Feed efficiency } & 0.34 \\\text { Milk yield } & 0.30 & \\\text { Calving interval } & 0.01 &\end{array}$$
a)Which of these traits would be most responsive to artificial selection?
b)Which would be least responsive?

Question 34

An individual plant is heterozygous for loci that affect height and have a strictly additive mode of action.If this plant is selfed,:
a)how many height classes will there be among the progeny? (Assume no environmental effects.)
b)what will be the frequency of the tallest class of progeny? (Assume no environmental effects.)

Question 35

In the course of estimating the degree of linkage of a marker and a quantitative trait of interest,researchers announced that they obtained a LOD score of 4.5.This finding indicates that:

A)there is a 4.5% chance that an individual with the marker will also show the trait of interest.
B)the marker is 4.5 map units away from the QTL controlling the trait of interest.
C)the marker is most likely not linked to the QTL controlling the trait of interest.
D)the odds that the marker is linked to the QTL controlling the trait of interest are 4.5:1.
E)the odds that the marker is linked to the QTL controlling the trait of interest are 4500:1.

Question 36

Two highly inbred populations of the annual weed Capsella bursa-pastoris grow in adjacent fields.One field is mowed regularly;the other is never mowed.Seeds from the plants are taken to a greenhouse where they can be grown under uniform conditions.The mean height of plants at the time of flowering is measured for each population,and for the F₁ and F₂ generations from crosses between representatives of each population.The data from these experiments are as follows:
$\begin{array}{|l|r|r|}\hline& \text { Mean } & \text { Variance } \\&\text { (in cm) } &\\\hline \text { Mowed Field } & 6.2 & 4.0 \\\hline \text { Unmowed Field } & 13.6 & 10.2 \\\hline F_{1} & 10.2 & 12.6 \\\hline F_{2} & 10.4 & 20.3 \\\hline\end{array}$

a)How much of the observed variance in plant height at flowering is caused by the environment in which the plants are grown?
b)How much of the variance is due to genotype?
c)What is the broad-sense heritability (H²)for this character?