Question 1

One reason that the effects of individual genes on complex traits can be difficult to determine is that:

Accepted Answer

A) environmental effects cannot be measured. 
B) environmental effects are so large that genetic effects cannot be measured. 
C) a single phenotype may be produced by many different genotypes. 
D) neither environmental nor genetic effects can be measured. 
E) genetic effects cannot be measured, regardless of the effects of the environment. 
A) environmental effects cannot be measured. 
B) environmental effects are so large that genetic effects cannot be measured. 
C) a single phenotype may be produced by many different genotypes. 
D) neither environmental nor genetic effects can be measured. 
E) genetic effects cannot be measured, regardless of the effects of the environment.

Question 2

Consider Figure 18.11, below, which shows the incidence of the most common birth anomalies. Why does the pie chart NOT include behavioral disorders such as autism spectrum disorder?

Accepted Answer

A) Genes do not influence behavioral traits. 
B) Genes affecting behavioral traits do not differ among individuals. 
C) Genes affecting behavioral traits have very small effects. 
D) Behavioral disorders are not detected at birth. 
E) None of the answer options is correct. 
A) Genes do not influence behavioral traits. 
B) Genes affecting behavioral traits do not differ among individuals. 
C) Genes affecting behavioral traits have very small effects. 
D) Behavioral disorders are not detected at birth. 
E) None of the answer options is correct.

Question 3

Consider a simple Mendelian trait that is due to a single gene with alleles A and a. In one environment, allele A is dominant, whereas in a different environment allele a is dominant. This is an example of:

Accepted Answer

A) a complex trait. 
B) epistasis. 
C) genotype-by-environment interaction. 
D) genotype-by-environment discordance. 
A) a complex trait. 
B) epistasis. 
C) genotype-by-environment interaction. 
D) genotype-by-environment discordance.

Question 4

For which of the following traits do genetic risk factors transmitted from parent to offspring NOT play a major role in the development of the trait?

Accepted Answer

A) autism 
B) clinical depression 
C) handedness 
D) blood pressure 
E) epilepsy 
A) autism 
B) clinical depression 
C) handedness 
D) blood pressure 
E) epilepsy

Question 5

A scientist measured heritability in yield per acre of a strain of wheat grown on a farm in eastern Europe and determined that it was 80%. She can therefore conclude that:

Accepted Answer

A) 80% of variation among individuals when the same strain of wheat is grown in Nebraska will be due to genetic differences. 
B) 80% of variation among individuals when the same strain of wheat is grown on the same farm in eastern Europe the following year will be due to genetic differences. 
C) when the same strain of wheat is grown on two different farms at the same time, 80% of the average difference in yield per acre will be due to genetic differences among populations. 
D) 80% of the total yield is due to genotype and 20% to environment. 
E) None of the answer options is correct. 
A) 80% of variation among individuals when the same strain of wheat is grown in Nebraska will be due to genetic differences. 
B) 80% of variation among individuals when the same strain of wheat is grown on the same farm in eastern Europe the following year will be due to genetic differences. 
C) when the same strain of wheat is grown on two different farms at the same time, 80% of the average difference in yield per acre will be due to genetic differences among populations. 
D) 80% of the total yield is due to genotype and 20% to environment. 
E) None of the answer options is correct.

Question 6

If all variation among individuals in a population is due to differing environments, heritability is _____, and the slope of the line used to measure it is _____.

Accepted Answer

A) 100%; 0.5 
B) 100%; 1 
C) 50%; 0.5 
D) 50%; 1 
E) 0; 0 
A) 100%; 0.5 
B) 100%; 1 
C) 50%; 0.5 
D) 50%; 1 
E) 0; 0

Question 7

Five varieties of hybrid corn are studied for average yield of corn (the phenotype) as a function of annual rainfall (the environment), with the results shown here.   Each of these lines constitutes a:

Accepted Answer

A) normative assessment. 
B) genotype-by-environment interaction. 
C) normalizing transformation. 
D) normal curve of error. 
E) norm of reaction. 
A) normative assessment. 
B) genotype-by-environment interaction. 
C) normalizing transformation. 
D) normal curve of error. 
E) norm of reaction.

Question 8

Red coloration in wheat seeds is a complex trait influenced by three unlinked genes, each with two different alleles A and a; B and b; C and c. This Punnett square shows the results of a mating between two plants that are both heterozygous at all three genes.   Each dominant allele, represented by an uppercase letter, contributes to the red coloration.

Accepted Answer

A) True 
 B)False

Question 9

Sunlight exposure has stronger effect on skin cancer risk in fair-skinned humans than in individuals with darker skin. This is an example of:

Accepted Answer

A) pleiotropy. 
B) epistasis. 
C) genotype-by-environment interaction. 
D) differences in the norm of reaction. 
E) All of these choices are correct. 
A) pleiotropy. 
B) epistasis. 
C) genotype-by-environment interaction. 
D) differences in the norm of reaction. 
E) All of these choices are correct.

Question 10

Identification and location of genes on chromosomes that might affect cholesterol metabolism has been difficult because many of the genes that affect this trait interact, a phenomenon that is called epistasis.

Accepted Answer

A) True 
 B)False

Question 11

Inbred lines show:

Accepted Answer

A) no phenotypic variation. 
B) phenotypic variation due to genetic variation. 
C) phenotypic variation due to environmental variation. 
D) phenotypic variation due to genotype-by-environment interaction. 
E) None of the answer options is correct. 
A) no phenotypic variation. 
B) phenotypic variation due to genetic variation. 
C) phenotypic variation due to environmental variation. 
D) phenotypic variation due to genotype-by-environment interaction. 
E) None of the answer options is correct.

Question 12

In the graph of Galton's height data below, which line on the graph represents the population mean?

Accepted Answer

A) line a 
B) line b 
C) line c 
A) line a 
B) line b 
C) line c

Question 13

A premise of personalized medicine is that two people:

Accepted Answer

A) can develop the same condition for different reasons. 
B) with the same disease likely share similar genotypes. 
C) with the same disease likely share common risk factors. 
D) with the same disease are likely to respond similarly to similar medications. 
E) with the same disease are highly unlikely to respond to similar medications. 
A) can develop the same condition for different reasons. 
B) with the same disease likely share similar genotypes. 
C) with the same disease likely share common risk factors. 
D) with the same disease are likely to respond similarly to similar medications. 
E) with the same disease are highly unlikely to respond to similar medications.

Question 14

Clustering of genes with related functions on the same chromosome reflects the fact that many genes arose through the process of duplication of a single gene, followed by divergence.

Accepted Answer

A) True 
 B)False

Question 15

An example of "regression toward the mean" would be if the offspring of two short parents had an average height equal to the average height of the parentsF1F1F1S1F1F1F10not of the population as a whole.

Accepted Answer

A) True 
 B)False

Question 16

Some tentative patterns that are emerging from the study of complex traits are that:

Accepted Answer

A) many genes involved in complex traits are pleiotropic. 
B) many genes involved in complex traits show epistasis. 
C) most genes affecting complex traits have minor effects; few have major effects. 
D) genes involved in complex traits usually show pleiotropy or epistasis. 
E) genes involved in complex traits can show pleiotropy or epistasis, and most have major effects. 
A) many genes involved in complex traits are pleiotropic. 
B) many genes involved in complex traits show epistasis. 
C) most genes affecting complex traits have minor effects; few have major effects. 
D) genes involved in complex traits usually show pleiotropy or epistasis. 
E) genes involved in complex traits can show pleiotropy or epistasis, and most have major effects.

Question 17

The phenotypes of complex traits vary with both genotype and environment. An important implication of this is that:

Accepted Answer

A) we can't predict the expression of a genotype without knowing its environment. 
B) we can't predict how a given environment will affect the expression of a trait without knowing its genotype. 
C) no one genotype will produce the "best" phenotype in all environments. 
D) several different genotypes may produce equally fit phenotypes in the same environment. 
E) All of these choices are correct. 
A) we can't predict the expression of a genotype without knowing its environment. 
B) we can't predict how a given environment will affect the expression of a trait without knowing its genotype. 
C) no one genotype will produce the "best" phenotype in all environments. 
D) several different genotypes may produce equally fit phenotypes in the same environment. 
E) All of these choices are correct.

Question 18

The data in the graph below show the concordance between identical twins (monozygotic) and same-sex fraternal twins (dizygotic) for five complex traits. Based on these data, which of the traits shows the GREATEST effect of environment relative to heredity?

Accepted Answer

A) trait M 
B) trait H 
C) trait K 
D) trait L 
E) trait Q 
A) trait M 
B) trait H 
C) trait K 
D) trait L 
E) trait Q

Question 19

The overall results represented in Figure 18.7 suggest that offspring exhibit an average phenotype that is more different from the population mean than that of their parents.

Accepted Answer

A) True 
 B)False

Question 20

Which of the following are complex traits in humans?

Accepted Answer

A) depression 
B) height 
C) autism 
D) cystic fibrosis 
A) depression 
B) height 
C) autism 
D) cystic fibrosis

Exam 18: The Genetic and Environmental Basis of Complex Traits

One reason that the effects of individual genes on complex traits can be difficult to determine is that:

Consider Figure 18.11, below, which shows the incidence of the most common birth anomalies. Why does the pie chart NOT include behavioral disorders such as autism spectrum disorder?

Consider a simple Mendelian trait that is due to a single gene with alleles A and a. In one environment, allele A is dominant, whereas in a different environment allele a is dominant. This is an example of:

For which of the following traits do genetic risk factors transmitted from parent to offspring NOT play a major role in the development of the trait?

A scientist measured heritability in yield per acre of a strain of wheat grown on a farm in eastern Europe and determined that it was 80%. She can therefore conclude that:

If all variation among individuals in a population is due to differing environments, heritability is _____, and the slope of the line used to measure it is _____.

Five varieties of hybrid corn are studied for average yield of corn (the phenotype) as a function of annual rainfall (the environment), with the results shown here. Each of these lines constitutes a:

Sunlight exposure has stronger effect on skin cancer risk in fair-skinned humans than in individuals with darker skin. This is an example of:

Identification and location of genes on chromosomes that might affect cholesterol metabolism has been difficult because many of the genes that affect this trait interact, a phenomenon that is called epistasis.

Inbred lines show:

In the graph of Galton's height data below, which line on the graph represents the population mean?

A premise of personalized medicine is that two people:

Clustering of genes with related functions on the same chromosome reflects the fact that many genes arose through the process of duplication of a single gene, followed by divergence.

An example of "regression toward the mean" would be if the offspring of two short parents had an average height equal to the average height of the parentsnot of the population as a whole.

Some tentative patterns that are emerging from the study of complex traits are that:

The phenotypes of complex traits vary with both genotype and environment. An important implication of this is that:

The data in the graph below show the concordance between identical twins (monozygotic) and same-sex fraternal twins (dizygotic) for five complex traits. Based on these data, which of the traits shows the GREATEST effect of environment relative to heredity?

The overall results represented in Figure 18.7 suggest that offspring exhibit an average phenotype that is more different from the population mean than that of their parents.

Which of the following are complex traits in humans?

Life: Chemical, Cellular, and Evolutionary Foundations

The Molecules of Life

Nucleic Acids and Transcription

Translation and Protein Structure

Organizing Principles: Lipids, Membranes, and Cell Compartments

Making Life Work: Capturing and Using Energy

Cellular Respiration: Harvesting Energy From Carbohydrates and Other Fuel Molecules

Photosynthesis: Using Sunlight to Build Carbohydrates

Cell Signaling

Cell and Tissue Architecture: Cytoskeleton, Cell Junctions, and Extracellular Matrix

Cell Division: Variations, Regulation, and Cancer

Dna Replication and Manipulation

Genomes

Mutation and Dna Repair

Genetic Variation

Mendelian Inheritance

Inheritance of Sex Chromosomes, Linked Genes, and Organelles

Genetic and Epigenetic Regulation

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Evolution: How Genotypes and Phenotypes Change Over Time

Species and Speciation

Evolutionary Patterns: Phylogeny and Fossils

Human Origins and Evolution

Cycling Carbon

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Eukaryotic Cells: Origins and Diversity

Being Multicellular

Plant Structure and Function: Moving Photosynthesis Onto Land

Plant Reproduction: Finding Mates and Dispersing Young

Plant Growth and Development

Plant Defense: Keeping the World Green

Plant Diversity

Fungi: Structure, Function, and Diversity

Animal Nervous Systems

Animal Sensory Systems and Brain Function

Animal Movement: Muscles and Skeletons

Animal Endocrine Systems

Animal Cardiovascular and Respiratory Systems

Animal Metabolism, Nutrition, and Digestion

Animal Renal Systems: Water and Waste

Animal Reproduction and Development

Animal Immune Systems

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Animal Behavior

Population Ecology

Species Interactions, Communities, and Ecosystems

Biomes and Global Ecology

The Anthropocene: Humans As a Planetary Force

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If all variation among individuals in a population is due to differing environments, heritability is _, and the slope of the line used to measure it is _.