Deck 14: Human Genetics and Variation

Question 1

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

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

Answer 1

A

Question 2

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

Answer 2

A

Question 3

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) are entirely environmental.

Answer 3

C

Question 4

Non-insulin-dependent diabetes (NIDD) may be an example of a(n)

A) trait that conferred a benefit in the past but is no longer beneficial.
B) trait that was maladaptive in the past but now confers a significant benefit.
C) genetic trait that can be beneficial or not depending on the presence or absence of malaria parasites.
D) environmentally caused disease that has a genetically based cure.

Question 5

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

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

Question 6

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) mutations that cause novel genes to arise.

Question 7

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) variation in the environment over time caused by climate change.

Question 8

Which of the following describes sickle-cell anemia?

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

Question 9

The normal modern human version of the FOXP2 gene spread throughout human populations less than ________ years ago.

A) 10,000
B) 500,000
C) 200,000
D) 75,000

Question 10

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 people's teeth 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 11

Assume specific language impairment (SLI) can be caused by a dominant allele. 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%

Question 12

Environmental variation includes factors such as differences in

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

Question 13

Tay-Sachs disease may give partial resistance to tuberculosis

A) in adults who are homozygous.
B) and may be an example of a balanced polymorphism.
C) and is absent in Jews of Eastern European ancestry, causing them to be more susceptible to the disease.
D) but increases susceptibility to malaria.

Question 14

Evidence 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 15

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 16

Variation refers to ________ between individuals or populations of individuals.

A) differences
B) only genetic differences
C) only environmental differences
D) only cultural differences

Question 17

Which of the following statements about the FOXP2 gene is correct?

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

Question 18

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

Question 19

Which of the following statements correctly describes non-insulin-dependent diabetes?

A) It was a seriously deleterious trait in the past and therefore no longer exists.
B) It causes blood-sugar levels to rise above normal because the cells of the body do not respond properly to hemoglobin.
C) It has no known genetic basis.
D) It is caused by the same genetic mutation that causes sickle-cell disease.

Question 20

Different human groups

A) have the same potential for the known genetic diseases.
B) all have the same potential for most diseases, but for some groups the disease is environmental; for others, it is genetic.
C) vary in the incidence of many genetically transmitted diseases.
D) have similar genetic diseases but vary in how the diseases are accepted culturally.

Question 21

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 22

________ tends to blur the effects of population expansions.

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

Question 23

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 24

A selection-mutation balance occurs when

A) mutation introduces alleles that selection favors for one reason, even if the alleles also cause a trait that is deleterious.
B) mutation introduces deleterious recessive alleles at a rate that is similar to or higher than the rate at which selection removes the alleles.
C) a large number of deleterious mutations occur over a short period of time, and there is no subsequent selection against them.
D) a beneficial mutation arises and spreads for a specific period of time, then the mutation becomes deleterious in a new environment and is removed by selection over a similar period of time.

Question 25

If the frequency of an allele is 0.01, what are the chances of observing a homozygote in the next generation (if the population is in Hardy-Weinberg equilibrium)?

A) 0.10
B) 0.01
C) 0.001
D) 0.0001

Question 26

Lactase persistence 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

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 28

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 29

A balanced polymorphism is a

A) balance between mutation and selection.
B) balance between selection and drift.
C) state in which two alleles remain in a population because of heterozygote advantage.
D) state in which environmental and genetic causes of a trait (a "morph") are roughly equal.

Question 30

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 31

Variation among groups at a single locus can be maintained by

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

Question 32

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 33

Selection can maintain variation within populations if heterozygotes

A) are excluded from the population by environmental factors.
B) are increased in number by fixation.
C) mutate into homozygotes at the same rate as they form.
D) have higher fitness than either of the two homozygotes for a given gene.

Question 34

Variation among groups at a single locus can be maintained by

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

Question 35

Heritability is the

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

Question 36

Environmental covariation refers to the

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

Question 37

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 38

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 39

Deleterious alleles 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 40

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 41

Genetic variation within local groups reflects about ________ of the genetic variation in the human species.

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

Question 42

Variation in height is heritable within groups. Therefore, ________ height differences among groups.

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

Question 43

Race is a(n)

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

Question 44

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 45

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 46

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

Question 47

Twin studies assume that

A) the fetal environments of monozygotic and dizygotic twins are equally similar.
B) the early postnatal environments of monozygotic and dizygotic twins diverge quickly.
C) monozygotic twins share fewer genes.
D) dizygotic twins are essentially the same as nontwin siblings in both genetic and environmental factors.

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

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

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

Question 50

Why are there many deleterious, often fatal, recessive alleles found at low frequencies in human populations?

Question 51

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 52

Genetic results for so-called 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 53

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 54

Classification of people in Brazil

A) is based on stature rather than skin color.
B) uses "color," but the term only refers to hair color.
C) is based on a presumption of ancestry that has been shown to be incorrect.
D) reflects genetic ancestry accurately, but is still unfair.

Question 55

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 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

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

Question 58

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 59

Most genetic variation exists

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

Question 60

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

A) selection for taller people, who do better in the modern world.
B) more extensive exercise in professional gyms.
C) an increase in available food and decrease in disease.
D) walking and running being replaced by driving.

Question 61

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

Question 62

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

Question 63

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 64

Describe and contrast selection and genetic drift as two major causes of genetic variation among human groups.

Question 65

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

Question 66

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. Can you argue that this variation that you observe due solely to genetics? Why or why not? How would you test the hypothesis that stature in each of these two groups is genetic?

Question 67

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

Question 68

How are modern humans genetically different from the chimpanzee?