Deck 18: Population and Evolutionary Genetics

Question 1

A Mendelian population is defined by individuals as:

A)interbreeding.
B)inbreeding.
C)evolving.
D)segregating.
E)migrating.

Answer 1

A

Question 2

Suppose that in a population the frequency of a particular recessive condition is 1/400.Assume the presence of only a dominant allele (A)and a recessive allele (a)in the population and that the population is at Hardy-Weinberg equilibrium.What is the frequency of heterozygotes in the population?

A)0)0025
B)0)05
C)0)095
D)0)9025
E)0)0475

Answer 2

C

Question 3

The _____ is all of the genetic information within a Mendelian population.

A)effective population size
B)Hardy-Weinberg equilibrium
C)fitness
D)genotypic frequency
E)gene pool

Answer 3

E

Question 4

Differential reproduction of genotypes leads to evolution via what process?

A)Inbreeding
B)Natural selection
C)Genetic rescue
D)Genetic drift
E)Mutational load

Question 5

A population that goes through a dramatic reduction in size will experience:

A)an effective population size.
B)Hardy-Weinberg equilibrium.
C)a genetic rescue.
D)a genetic bottleneck.
E)inbreeding depression.

Question 6

When an allele has a frequency of 1.0 in a population, it is _____ in the population.

A)lost
B)dominant
C)overdominant
D)fixed
E)recessive

Question 7

What effect does mutation have on a population?

A)It creates or increases genetic variation.
B)It promotes the fixation of alleles.
C)It reduces the amount of genetic variation.
D)It homogenizes genetic variation across populations.
E)It increases rates of outcrossing.

Question 8

Which of the following evolutionary forces does NOT normally change allele frequencies?

A)Nonrandom mating
B)Mutation
C)Selection
D)Drift
E)Migration

Question 9

DNA typing is used to compare evidence DNA (E)left at a crime scene to two suspects (S1 and S2).Suspect 1 is excluded by the evidence, but suspect 2 remains included.What is the frequency of suspect 2's genotype if the allele frequencies in the population are f(A₁)= 0.1, f(A₂)= 0.2, and f(A₃)= 0.7 and the population is at Hardy-Weinberg equilibrium?

A)0)01
B)0)02
C)0)04
D)0)28
E)0)49

Question 10

Suppose that in a population the frequency of a particular recessive condition is 1/400.Assume the presence of only a dominant allele (A)and a recessive allele (a)in the population and that the population is at Hardy-Weinberg equilibrium.What is the frequency of the recessive allele that causes the condition?

A)0)000625
B)0)0025
C)0)025
D)0)05
E)0)95

Question 11

One way to define _____ is any change in allele frequencies within a population.

A)mutation
B)natural selection
C)equilibrium
D)evolution
E)sampling error

Question 12

_____ increases the frequency of homozygotes in a population compared to the results of random mating.

A)Inbreeding
B)Migration
C)Outcrossing
D)Genetic drift
E)Directional selection

Question 13

Which of the following does NOT bring about evolution in a population?

A)Small population size
B)Migration of individuals from a population with a different genetic structure
C)Mutation
D)Selection
E)Random mating

Question 14

_____ has the effect of homogenizing allele frequencies among populations.

A)Migration
B)Sampling error
C)Directional selection
D)Assortative mating
E)Selection-mutation equilibrium

Question 15

If there is random mating in a population and no evolutionary forces are acting on the population, what will be the expected outcome?

A)The allele frequencies will remain the same, but the genotype distribution will change.
B)The genotype distribution will remain the same, but the allele frequencies will change.
C)Both the genotype distribution and the allele frequencies will change.
D)Both the genotype distribution and the allele frequencies will remain the same.
E)No prediction can be made about the genotype distribution and allele frequencies from one generation to the next.

Question 16

In overdominance, the HIGHEST fitness is found in which genotype?

A)Homozygote for the dominant allele
B)Homozygote for the recessive allele
C)Heterozygote
D)Mutant
E)Inbred recessive

Question 17

When considering the gene pool of a population, Hardy-Weinberg equilibrium may apply to:

A)only the entire genome but not individual loci.
B)one locus but not necessarily another.
C)dominant and recessive alleles, but not codominant alleles.
D)only to the effective number of breeders.
E)only autosomal but not X-linked loci.

Question 18

The only way for evolution to take place is if there is _____ within a population.

A)nonrandom mating
B)natural selection
C)genetic drift
D)Hardy-Weinberg equilibrium
E)genetic variation

Question 19

_____ is the product of sampling errors and chance events that may result in changes in allele frequencies.

A)Mutation
B)Genetic drift
C)Directional selection
D)Inbreeding
E)Evolution

Question 20

If there are two alleles, A and a, in a population and the population is at Hardy-Weinberg equilibrium, which frequency of A would produce the greatest frequency of heterozygotes?

A)0)1
B)0)25
C)0)5
D)0)75
E)1

Question 21

Of the various evolutionary forces, _____ is responsible for the origin of new genetic variation in a species.

A)natural selection
B)genetic drift
C)mutation
D)migration
E)nonrandom mating

Question 22

_____ refers to the situation where the heterozygote has a lower fitness than both homozygotes (W₁₁ > W₁₂ < W₂₂).

A)Overdominance
B)Hardy-Weinberg equilibrium
C)Underdominance
D)Heterozygote superiority
E)Genetic rescue

Question 23

Which agent of evolution is MOST likely responsible for the decrease in the frequency of a recessive allele as shown in the graph below?

A)Genetic drift
B)Natural selection
C)Mutation
D)Assortative mating
E)Inbreeding

Question 24

_____ is the movement of genes between populations.

A)Evolution
B)Migration
C)Positive assortative mating
D)Outcrossing
E)Genetic drift

Question 25

_____ is BEST known for developing the concept of biological species.

A)Lewontin
B)Darwin
C)Mayr
D)Fisher
E)Bush

Question 26

The neutral-mutation hypothesis suggests all of the following EXCEPT:

A)the evolution of most genetic variation in a population is influenced by genetic drift.
B)when natural selection is at work on protein variants, it will lead to little variation in the population.
C)most molecular variation is adaptively neutral-for example, most protein variants are functionally equivalent.
D)natural selection is still an important evolutionary force.
E)genetic variation in a population is maintained mainly by natural selection.

Question 27

A variation on the _____ model of speciation is when a small group of individuals colonizes an island.

A)autocratic
B)allopatric
C)sympatric
D)parapatric
E)peripatric

Question 28

_____ is the splitting of one lineage into two.

A)Genesis
B)Anagenesis
C)Phylogenesis
D)Cladogenesis
E)Neogenesis

Question 29

Through _____, alleles may disappear from a population simply by chance.

A)negative directional selection
B)genetic rescue
C)genetic drift
D)fixation
E)underdominance

Question 30

The evolutionary force of _____ tends to increase genetic variation within a population but decrease genetic variation between populations, while the evolutionary force of _____ tends to decrease genetic variation within a population but increase genetic variation among populations.

A)migration; genetic drift
B)mutation; some types of natural selection
C)genetic drift; migration
D)some types of natural selection; mutation
E)positive assortative mating; negative assortative mating

Question 31

Which agent of evolution tends to reduce genetic variation between populations and increase genetic variation within each population?

A)Natural selection
B)Mutation
C)Migration
D)Inbreeding
E)Genetic drift

Question 32

_____ is when the heterozygote has a higher fitness than either of the two homozygotes (W₁₁ < W₁₂ > W₂₂).Allele frequencies will change in this population until _____.

A)Underdominance; an allele is fixed
B)Homeostasis; Hardy-Weinberg equilibrium is achieved
C)Dominance; a tipping point is passed
D)Recombination; linkage equilibrium is obtained
E)Overdominance; a stable equilibrium is reached

Question 33

Rapid changes in allelic frequencies by _____ take place in populations that are small.

A)mutation
B)natural selection
C)inbreeding
D)outbreeding
E)genetic drift

Question 34

_____ ultimately produces all new genetic variation in a population.

A)Outcrossing
B)Migration
C)Evolution
D)Mutation
E)Equilibrium

Question 35

_____ is the idea that, if postzygotic isolating mechanisms exist between two species, then natural selection will favor traits that lead to the evolution of prezygotic isolating mechanisms.

A)Hybrid breakdown
B)Reinforcement
C)Gametic isolation
D)Phylogenetic species
E)Hybrid inviability

Question 36

Evolution can be defined as _____ change that takes place in a(n)_____.

A)any; individual
B)a genetic; individual
C)any; group of organisms
D)a genetic; group of organisms
E)All of the answers are correct.

Question 37

The _____ concept defines a species as a group of organisms that are capable of exchanging genes.

A)morphospecies
B)phylogenetic species
C)biological species
D)cladogenic species
E)evolutionary species

Question 38

_____ occurs when one allele or trait is favored over another.

A)Directional selection
B)Mutation-selection equilibrium
C)Founder effects
D)Stabilizing selection
E)Overdominance

Question 39

_____ speciation arises in the absence of any geographic barrier to gene flow.

A)Autocratic
B)Allopatric
C)Sympatric
D)Parapatric
E)Peripatric

Question 40

Problems with using the biological species concept include all of the following EXCEPT:

A)it is sometimes difficult to determine if reproductive isolation exists.
B)reproductive isolation does not apply to asexual organisms.
C)the concept of reproductive isolation does not work for fossils.
D)reproductive isolation is not a mechanism that ensures that species are evolving independently.
E)None of the answers is correct.

Question 41

_____ characteristics evolved from the same character in a common ancestor.

A)Similar
B)Paralogous
C)Homologous
D)Phylogenetic
E)Parsimonious

Question 42

All of the following are examples of prezygotic reproductive isolating mechanisms EXCEPT:

A)a cat trying to mate with a lion.
B)a male fiddler crab waving its claw to attract a mate.
C)the hybrid offspring of two species dying before birth.
D)fireflies flashing their light-emitting organs.
E)two plant species flowering at different times.

Question 43

All of the following are examples of postzygotic reproductive isolating mechanisms EXCEPT:

A)a sheep adapted to mountains mating with a sheep adapted to desert, producing offspring maladapted to either habitat.
B)two plant species flowering at different times.
C)the hybrid offspring of two species dying before birth.
D)the hybrid offspring of two species being sterile.
E)the hybrid offspring of two species being fertile but their offspring being inviable or sterile.

Question 44

For most protein-coding genes, the rate of substitution in _____ is considerably higher than in _____.

A)synonymous sites; nonsynonymous sites
B)nonsynonymous sites; synonymous sites
C)nonsynonymous sites; introns
D)3' untranslated regions; synonymous sites
E)3' untranslated regions; introns

Question 45

A(n)_____ tree is one that contains an internal node representing the common ancestor to all other nodes in the tree.

A)gene
B)phylogenetic
C)outgroup
D)most parsimonious
E)rooted

Question 46

How might gene duplication provide a mechanism for the addition of new genes with novel functions?

Question 47

Is the buildup of reproductive barriers in two allopatric populations the result of natural selection for reproductive isolation?

Question 48

Based on careful inspection of the genetic code, why might the second position of a codon have the lowest rate of substitutions in a gene?

Question 49

_____ represent the evolutionary relationships among groups of organisms.

A)Alignments
B)Nodes
C)Synonymous rates of substitution
D)Phylogenetic trees
E)Species concepts

Question 50

The relatively small amount of genetic differentiation among some species suggests that many phenotypic differences reflect changes in _____ rather than the evolution of new genes.

A)gene expression
B)gene duplication
C)exon shuffling
D)whole-genome duplication
E)horizontal gene transfer

Question 51

For most protein-encoding genes, the synonymous rate of change is considerably higher than the nonsynonymous rate.In comparing two taxa, how might you interpret the evolutionary history of a gene if the nonsynonymous rate of change was higher than the synonymous rate?

Question 52

Horizontal gene transfer is MOST common:

A)among bacteria.
B)among eukaryotes.
C)among viruses.
D)from eukaryotes to bacteria.
E)from plants to animals.

Question 53

Which region of a gene should have the highest rates of substitution?

A)First position of a codon
B)Second position of a codon
C)Third position of a codon
D)5' flanking region
E)3' untranslated region

Question 54

Because real-life populations are, of course, not infinitely large, why is the Hardy-Weinberg condition of an "infinitely large population" usually met for natural populations?

Question 55

The Hardy-Weinberg law (equation)is a mathematical model in which allele frequencies in populations remain constant from generation to generation.Given all the conditions that must be met for the Hardy-Weinberg equation to be valid, why is this equation useful for studying population genetics?

Question 56

What two factors are thought to play a critical role in sympatric speciation? Explain how they lead to sympatric speciation.

Question 57

Genetic diseases in humans are usually rare and recessive.Why are the frequencies of alleles that cause rare, recessive diseases (or other recessive traits, for that matter)generally much higher than the frequency of the diseases (or traits)themselves?

Question 58

The _____ approach to inferring relationships among species selects the phylogeny that minimizes the number of evolutionary changes.

A)maximum likelihood
B)parsimony
C)distance
D)rooted tree