Deck 14: Human Genetic Variation

Question 1

Genetic variation refers to

A) differences between individuals caused by the genes they inherit.
B) traits that are caused by the environment, not by genes.
C) traits that are caused by genes, not by the environment.
D) both a and

Answer 1

A

Question 2

According to the hypothesis the specific language impairment (SLI) can be caused by a dominant gene at a single locus, what is the probability that an individual who has SLI and an individual without it will have a child with SLI?

A) 0%
B) 75%
C) 50%
D) 100%

Answer 2

C

Question 3

Scientists conventionally divide human variation into which two components?

A) Genetic and cultural
B) Cultural and environmental
C) Genetic and environmental
D) Cultural and phenotypic

Answer 3

C

Question 4

Variation refers to

A) differences between individuals or populations of individuals.
B) only genetic differences between individuals or populations of individuals.
C) only environmental differences between individuals or populations of individuals.
D) only cultural differences between individuals or populations of individuals.

Question 5

Non-insulin-dependent diabetes

A) was a maladaptive trait in the past.
B) causes iron levels to rise above normal because the cells of the body do not respond properly to hemoglobin.
C) has a genetic basis.
D) does not have a genetic basis.

Question 6

The evolution of lactase persistence in Africa and Europe was the result of

A) convergent adaptation.
B) drift acting on isolated populations.
C) gene flow between Africans and Europeans.
D) the retention of an ancestral trait.

Question 7

Sickle-cell anemia

A) is caused by a lack of protein.
B) is caused by a lack of iron.
C) causes unusually shaped red blood cells.
D) causes unusually shaped blood vessels.

Question 8

Where Plasmodium falciparum malaria is present, AS infants are about ________ more likely to reach adulthood than AA infants.

A) 100%
B) 50%
C) 35%
D) 15%

Question 9

If parents and offspring resemble each other, similarities are likely due to

A) shared genes.
B) shared genes and environments.
C) shared environment and culture.
D) shared genes, environments, and culture.

Question 10

The FOXP2 gene

A) causes a heritable disease called PKU.
B) changed in humans because of directional selection.
C) is an example of environmental variation.
D) is expressed in the tongue.

Question 11

Physical traits such as weight

A) are determined by genes more than by environment.
B) cannot be influenced by cultural practices.
C) can be influenced by genes, environment, and culture.
D) both a and

Question 12

Tay-Sachs disease may give partial resistance to tuberculosis

A) in heterozygous individuals.
B) and may be an example of a balanced polymorphism.
C) and occurs at a higher rate in Western European Jewish populations than in other Jewish populations.
D) both a and

Question 13

Human groups from different regions around the world

A) do not vary in terms of genetic diseases.
B) all have much the same genetic diseases.
C) vary in terms of genetic diseases.
D) both a and

Question 14

The normal version of the FOXP2 gene spread throughout human populations less than

A) 10,000 years ago.
B) 500,000 years ago.
C) 200,000 years ago.
D) 75,000 years ago.

Question 15

Evidence or proof that a trait is caused by a single gene includes

A) inheritance of Tay-Sachs disease in certain Jewish populations.
B) Hardy-Weinberg equilibrium.
C) observing a pattern of inheritance of dominant genes.
D) observing Mendelian inheritance patterns.

Question 16

Physical traits such as weight are

A) more determined by genes than by the environment.
B) determined by an interaction between genes and environment.
C) determined more by the environment than by genes.
D) strictly genetic.

Question 17

Environmental variation includes factors such as

A) differences in height.
B) differences in weight.
C) differences in genes.
D) differences in climate.

Question 18

We know that milk production played an important role in early pastoral communities in northern Europe because

A) analyses of their pottery show residues of compounds found only in milk.
B) isotopic analysis of the teeth of people shows they drank milk.
C) the amount of genetic diversity for milk proteins in domesticated cattle indicates that people kept small herds.
D) the amount of genetic diversity in domesticated cattle is greatest in southeastern Europe.

Question 19

Which of the following is (are) example(s) of variation among groups?

A) The distribution of Tay-Sachs among Jewish populations.
B) Differences in body weight between parents and their offspring.
C) Variation in height for college basketball players.
D) Variation in height and weight for jockeys.

Question 20

Environmental variation refers to

A) differences between individuals caused by environmental factors.
B) traits that are caused by the environment, not by genes.
C) traits that are caused by genes, not by the environment.
D) both a and

Question 21

Population expansions after the expansion of modern humans from Africa 60 kya include

A) an expansion of farming peoples between 4,000 and 1,000 years ago.
B) an expansion due to the domestication of the horse and associated military innovations between 5,000 and 10,000 years ago.
C) an expansion of European populations because of military organization during the last 4,000 years.
D) an expansion of seafaring people 1,000 years ago.

Question 22

Variation among groups at a single locus can be maintained by

A) haplotypes.
B) recombination.
C) founder effect.
D) single nucleotide polymorphisms.

Question 23

Monozygotic twins are

A) twins derived from two zygotes.
B) twins derived from a single zygote.
C) twins whose degree of relatedness is 0.5.
D) also known as "fraternal twins."

Question 24

A selection-mutation balance occurs when

A) mutation introduces alleles that selection favors.
B) mutation introduces alleles that selection does not favor.
C) selection is neutral and mutation is not present.
D) both b and

Question 25

Variation among groups at a single locus can be maintained by

A) different environments.
B) haplotypes.
C) single nucleotide polymorphisms.
D) recombination.

Question 26

The ability to digest lactose is controlled by

A) variation at a single locus.
B) variation at many loci.
C) factors not related to genetics.
D) a selective haplotype.

Question 27

Heritability is

A) the percentage of a trait determined by environment.
B) the proportion of observed variation due to genetic variation.
C) the extent to which genetic control of a trait is under the influence of selection.
D) the measure of how well genotype matches phenotype.

Question 28

Environmental covariation refers to

A) the difference between genetic and environmental variation.
B) the similarity between parents and offspring.
C) the similarity between the environments of parents and offspring.
D) the difference between parents and offspring.

Question 29

Variation may exist because environments have recently changed and genes that were previously beneficial have not yet been eliminated. This may describe

A) Tay-Sachs disease.
B) sickle-cell anemia.
C) non-insulin-dependent diabetes.
D) P. falciparum malaria.

Question 30

An example of a condition caused by genetic drift is

A) porphyria variegata.
B) non-insulin-dependent diabetes.
C) lactose tolerance.
D) cystic fibrosis.

Question 31

Deleterious alleles (lethal recessives) can remain at low frequencies in populations because

A) mutation can alter the allele to decrease its lethality.
B) most individuals who carry the gene are heterozygous and do not suffer consequences of having two copies of the gene.
C) heterozygotes most often pass on the dominant allele.
D) many, but not all, homozygous recessive individuals die.

Question 32

A balanced polymorphism is

A) a balance between mutation and selection.
B) a balance between selection and drift.
C) a state in which two alleles remain in a population because of heterozygote advantage.
D) either a or

Question 33

Researchers looking for signs of recent natural selection found changes in the coding genes that pertain to

A) hair texture.
B) morphology of the skull.
C) the immune system and affect human responses to viruses.
D) digestion and affect the metabolism of alcohol, carbohydrates, and fatty acids.

Question 34

Variation in the ability to digest lactose around the world is probably due to

A) genetic variation.
B) genetic drift.
C) different selective pressures.
D) both a and

Question 35

By searching DNA sequences for ________ that are common in a population, geneticists can find sequences that have been subject to recent selection.

A) long haplotypes
B) instances of founder effect
C) candidate genes
D) balanced polymorphisms

Question 36

Variation at a single locus can be maintained by

A) mutation.
B) heterozygote advantage.
C) mutation, but only if selection favors the gene also.
D) both a and

Question 37

________ tends to blur the effects of population expansions.

A) Mutation
B) Genetic drift
C) Gene flow
D) Founder effect

Question 38

The hemoglobin S allele causes sickle-cell anemia. It occurs in high frequencies

A) where pastoralism is common.
B) where drift has been strong.
C) where malaria is common.
D) where hemoglobin is rare.

Question 39

If the frequency of an allele is .01, what are the chances of observing a homozygote in the next generation (if the population is in Hardy-Weinberg equilibrium)?

A) .10
B) .01
C) .001
D) .0001

Question 40

A new beneficial mutation causes a(n) ________ in which both the mutation and the DNA linked to the mutation on the same chromosome spread throughout the population.

A) environmental covariation
B) specific language impairment
C) selective sweep
D) situation of negative selection

Question 41

Genetic results for "black" and "white" Brazilians reveals

A) that racial categories are consistent with genetic data.
B) little correlation between phenotype and ancestry.
C) that, although Brazilians can be categorized into race based on phenotype, they cannot be categorized genetically.
D) that folk classifications are genetically meaningful.

Question 42

Classifying humans into races is not possible because

A) genetic variation is continuous.
B) the placement of individuals within any single category is clear and obvious.
C) classifications based on different characters lead to consistent groupings.
D) race is not culturally relevant.

Question 43

The rates of change in the human lineage for highly accelerated regions of the genome that have undergone negative selection imply that they have been shaped by

A) genetic drift.
B) natural selection.
C) mutation.
D) sexual selection.

Question 44

Height and stature are

A) not heritable within most human populations.
B) heritable within human populations.
C) can change if environments change.
D) both b and

Question 45

To determine whether the differences between the human and chimpanzee genome are a result of natural selection or mutation and drift, geneticists compare synonymous and nonsynonymous substitutions. Genes that have evolved because of selection should show what pattern?

A) Fewer nonsynonymous substitutions than synonymous substitutions.
B) More nonsynonymous substitutions than synonymous substitutions.
C) No difference in nonsynonymous and synonymous substitutions.
D) There is too little information to answer this question.

Question 46

Body size varies among human groups. This variation may be caused in part by

A) twin studies.
B) heterozygote advantage.
C) mutation-selection balance.
D) selection.

Question 47

What percentage of protein-coding genes of humans and chimpanzees differ in a way that produces different proteins?

A) 10%
B) 30%
C) 50%
D) 70%

Question 48

________ do not produce any change in the amino acid sequence of a protein.

A) Transposable elements
B) Synonymous substitutions
C) Microsatellite loci
D) Highly accelerated regions

Question 49

Twin studies assume

A) that the early environments of monozygotic and dizygotic twins are equally similar.
B) that the fetal environments of monozygotic and dizygotic twins are equally similar.
C) that monozygotic twins share fewer genes.
D) both a and

Question 50

Which of the following statements about race is true?

A) The human species can be naturally divided into a small number of distinct races.
B) Members of different races are different in important ways, so that knowing a person's race gives you important information about what he or she is like.
C) Members of each race are genetically similar to each other, and genetically different from members of other races.
D) We cannot determine a discrete number of racial categories.

Question 51

An increase in stature coincided with modernization for many groups of people. This increase may be related to

A) less poverty.
B) more control of childhood diseases.
C) less environmental pollution.
D) both a and

Question 52

Classification of people in Brazil

A) includes the use of "smor."
B) reflects the ancestry of people.
C) reflects the same prejudices seen in North America.
D) reflects genetic variation.

Question 53

Most genetic variation exists

A) within local groups.
B) among local groups within races.
C) between races.
D) between local groups.

Question 54

If variation in a trait is largely due to variation in genes, then

A) monozygotic twins should be more similar to each other than dizygotic twins.
B) dizygotic twins should be more similar to each other than monozygotic twins.
C) monozygotic and dizygotic twins should be equally similar to one another.
D) dizygotic twins will be exactly alike.

Question 55

Humans and chimpanzees differ in about ________% of their total nucleotides.

A) 1.0
B) 2.5
C) 3.0
D) 0.75

Question 56

Researchers think that the negatively selected sequence HAR1

A) is related to the rapid evolution of the large and complex human brain.
B) has a slower rate of change in humans than in other lineages.
C) is found in a coding region and results in new proteins.
D) is involved in speech production along with FOXP2.

Question 57

In the opinion of the textbook authors, race is

A) a meaningful biological concept.
B) a biological reality only when the distribution of many genetic traits is considered.
C) a culturally constructed category.
D) an important tool for understanding human variation.

Question 58

Variation in height is heritable within groups. Therefore,

A) genetic differences cause height differences among groups.
B) environmental differences cause height differences among groups.
C) cultural differences cause height differences among groups.
D) genetic, environmental, or cultural differences may be responsible for height differences among groups.

Question 59

Most modern scientists studying human variation believe that humans can be divided into

A) three races: Caucasian, African, and Asian.
B) five races: Caucasian, African, Asian, American Indian, and indigenous Australian.
C) seven races: Caucasian, African, Asian, American Indian, Australian, Polynesian, and Oceanic.
D) one race: human.

Question 60

Genetic variation within local groups around the world contains about ________ of the genetic variation in the human species.

A) 5%
B) 35%
C) 85%
D) 95%

Question 61

How are modern humans genetically different from the chimpanzee?

Question 62

Explain the changes in the structural or protein-coding genes of humans and chimpanzees.

Question 63

Why are there many lethal recessives found at low frequencies in human populations?

Question 64

Choose a trait and describe how the three sources of variation can cause the trait to vary.

Question 65

Why is the hemoglobin S allele found in very high frequencies in some populations even though it is a lethal recessive?

Question 66

Discuss two major causes of genetic variation among human groups.

Question 67

Explain the rationale for, and assumptions of, using twins to estimate heritability.

Question 68

Although only a small fraction of protein-coding genes shows evidence of selection since the divergence of human and chimpanzee lineages, humans and chimpanzees are vastly different in their phenotypes. How can this be?

Question 69

Why is there variation between human populations in the ability to digest lactose? How has natural selection affected and maintained this variation?

Question 70

You have sampled height from two populations: the Maasai of East Africa and the Inuits of Alaska. You have determined that there is a significant difference in height between these two populations, with Inuits being of shorter height than the Maasai. Is this variation that you observe due solely to genetics? Why or why not?

Question 71

Why do scientists no longer believe that race is a meaningful biological concept?