Deck 23: Evolution of Genes and Genomes

Question 1

Below are short fragments of DNA sequences from two yeast strains (A and B), which have been diverging from each other, as well as a short fragment from their common ancestor (C). Yeast A: TGACTGCAAACATCCTAG
Yeast B: TGCCTGGACACATCGAAG
Yeast C: TGCCTGGAAACCTCCTAG
What type of information would best allow you to detect whether back substitutions occurred at any of the 18 nucleotides of the sequence as strain A evolved from the common ancestor?

A) Additional sequences from strain A from regions near the 18 nucleotides
B) Additional sequences from the ancestor from regions near the 18 nucleotides
C) Phenotypic data from strain A and the ancestor
D) The 18 nucleotides from yeast samples taken at various times between the ancestor and contemporary strain A
E) Sequence data from closely related strains

Answer 1

D

Question 2

In which order would a molecular evolutionist perform the following tasks: (1) construct a similarity matrix, (2) align the sequences, and (3) use a model of evolution to correct for multiple substitutions and other factors?

A) 1  2  3
B) 1  3  2
C) 2  1  3
D) 2  3  1
E) 3  2  1

Answer 2

C

Question 3

In an experiment, researchers split a bacterial colony in two, allowing each of the new colonies to evolve separately.They then sequence a gene from colony 1 and colony 2.In the common ancestor, at nucleotide site 327 there is G.In colony 1, there is C; in colony 2, there is C.This is an example of a _______ substitution.

A) single
B) coincident
C) parallel
D) back
E) multiple

Answer 3

C

Question 4

Below are short fragments of DNA sequences from two yeast strains (A and B), which have been diverging from each other, as well as a short fragment from their common ancestor (C). Yeast A: TGACTGCAAACATCCTAG
Yeast B: TGCCTGGACACATCGAAG
Yeast C: TGCCTGGAAACCTCCTAG
Based on the information from all three sequences, there is evidence for _______ parallel substitution(s) and _______ coincident substitution(s).

A) zero; one
B) one; zero
C) one; one
D) one; two
E) two; zero

Question 5

A hypothetical human protein sequence is 161 amino acids long.The homologous sequence in chimpanzees is 160 amino acids long.Which modification would most likely be needed to align the sequences?

A) A single substitution
B) A parallel substitution
C) A similarity matrix
D) A gap
E) An amino acid replacement

Question 6

Suppose three sibling species of frogs have the following DNA sequences at a portion of a gene: Species 1: AGTCTAGATCGCGGTCG
Species 2: AGTCGATCGCGGACG
Species 3: TGTCTAGATCACGGTCG
Recall that the observed number of mutations can differ from the total number of actual substitutions that occurred in pairwise sequence comparisons.If we assume that a gap of any length is equivalent to three nucleotide substitutions, how many substitutions have occurred between species 1 and species 3?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 7

Detection of _______ substitutions requires knowing the sequence of intermediates between the common ancestor and the descendant colonies, in addition to that of the two colonies and the common ancestor.

A) coincident
B) back
C) multiple
D) both coincident and back
E) both back and multiple

Question 8

Below are short fragments of DNA sequences from two yeast strains (A and B), which have been diverging from each other, as well as a short fragment from their common ancestor (C). Yeast A: TGACTGCAAACATCCTAG
Yeast B: TGCCTGGACACATCGAAG
Yeast C: TGCCTGGAAACCTCCTAG
Lacking information from the common ancestor, what would you conclude is the minimum number of evolutionary changes occurring between strains A and B?

A) three
B) four
C) five
D) six
E) seven

Question 9

Below are short fragments of DNA sequences from two yeast strains (A and B), which have been diverging from each other, as well as a short fragment from their common ancestor (C). Yeast A: TGACTGCAAACATCCTAG
Yeast B: TGCCTGGACACATCGAAG
Yeast C: TGCCTGGAAACCTCCTAG
What is the minimum number of evolutionary changes that have occurred between the common ancestor and strain A?

A) one
B) three
C) five
D) six
E) seven

Question 10

Which statement about molecular evolution is true?

A) Almost all genes evolve at the same rate.
B) All nucleotide substitutions give rise to amino acid replacements.
C) Changes in the amino acid sequence of a protein can change its charge but not its secondary structure.
D) Molecular evolution generates biological diversity.
E) Molecular evolution does not account for genetic variation.

Question 11

Genomes consist of

A) genes only.
B) genes and regulatory sequences only.
C) regulatory sequences only.
D) genes and noncoding DNA.
E) regulatory sequences and noncoding DNA only.

Question 12

Suppose three sibling species of frogs have the following DNA sequences at a portion of a gene: Species 1: AGTCTAGATCGCGGTCG
Species 2: AGTCGATCGCGGACG
Species 3: TGTCTAGATCACGGTCG
Recall that the observed number of mutations can differ from the total number of actual substitutions that occurred in pairwise sequence comparisons.Which modification would align the three sequences so they could be used to make comparisons?

A) Add a gap representing one nucleotide to Species 3 at the first nucleotide position.
B) Add a gap representing one nucleotide to Species 2 at the fifth nucleotide position.
C) Add a gap representing two nucleotides to Species 2 at the fifth nucleotide position.
D) Add a gap representing two nucleotides to Species 2 at the sixteenth nucleotide position.
E) None; no modification is needed.

Question 13

Which statement about a genome is false?

A) The genome must be replicated to be transmitted from parents to offspring.
B) Mutations can occur in the genome as a result of errors in DNA replication.
C) The genome is essentially a random collection of genes arranged in a random order along chromosomes.
D) In addition to the nuclear DNA, the genome also includes the DNA present in chloroplasts and mitochondria.
E) The positions of genes are subject to evolutionary change.

Question 14

A similarity matrix gives us a measure of the _______ number of changes that have occurred during divergence between pairs of organisms.

A) minimum
B) maximum
C) most likely
D) mean
E) median

Question 15

Below are short fragments of DNA sequences from two yeast strains (A and B), which have been diverging from each other, as well as a short fragment from their common ancestor (C).
Yeast A: TGACTGCAAACATCCTAG
Yeast B: TGCCTGGACACATCGAAG
Yeast C: TGCCTGGAAACCTCCTAG
What is the minimum number of evolutionary changes that have occurred since strains A and B evolved from their common ancestor?

A) three
B) four
C) five
D) six
E) seven

Question 16

In an experiment, researchers split a bacterial colony in two, allowing each of the new colonies to evolve separately.They then sequence a gene from colony 1 and colony 2.In the common ancestor, at nucleotide site 56 there is A.In colony 1, there is C; in colony 2, there is T.This is an example of a _______ substitution.

A) single
B) coincident
C) parallel
D) back
E) multiple

Question 17

A molecular evolutionist is collaborating with a researcher who wants to develop antibiotics that specifically bind to certain proteins on pathogenic chlamydia bacteria without harming beneficial bacteria in the host animal gut.The molecular evolutionary research approach that would best aid this project would be to investigate

A) why the genomes of different organisms vary in size.
B) how genomes acquire new functions.
C) the organization of genomes in different bacterial species.
D) the evolution of particular bacterial genes and their protein structures.
E) the rate of evolutionary changes in particular bacterial genes.

Question 18

In an experiment, researchers split a bacterial colony in two, allowing each of the new colonies to evolve separately.They then sequence a gene from colony 1 and colony 2.In the common ancestor, at nucleotide site 167 there is T.In colony 1, there is C; in colony 2, there is T.This is an example of a _______ substitution.

A) single
B) coincident
C) parallel
D) back
E) multiple

Question 19

Which comparison procedure would tend to make it easier to obtain correct sequence alignments?

A) Comparing distantly related species
B) Examining rapidly evolving sequences
C) Working with a segment of DNA that has frequent deletions
D) Working with a segment of DNA that has frequent insertions
E) Working with sequences of a gene from several species at different degrees of evolutionary relatedness to one another

Question 20

Suppose three sibling species of frogs have the following DNA sequences at a portion of a gene: Species 1: AGTCTAGATCGCGGTCG
Species 2: AGTCGATCGCGGACG
Species 3: TGTCTAGATCACGGTCG
Recall that the observed number of mutations can differ from the total number of actual substitutions that occurred in pairwise sequence comparisons.If we assume that a gap of any length is equivalent to three nucleotide substitutions, how many substitutions have occurred between Species 1 and Species 2?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 21

Refer to the table and sequence. If C were substituted for the nucleotide in position 4 (highlighted) of the sequence, this would be characterized as a _______ nucleotide substitution.

A) nonsynonymous
B) synonymous
C) deleterious
D) missense
E) nonsense

Question 22

The occurrence of which event(s) usually does not lead to an undercounting of the real number of substitutions?

A) Parallel substitutions
B) Back substitution
C) Single substitution
D) Multiple substitutions
E) Coincident substitutions

Question 23

Refer to the table and sequences. According to the genetic code, the nucleotide substitution in the highlighted position of sequence 2 is a _______ nucleotide substitution.

A) nondeleterious
B) synonymous
C) silent
D) missense
E) nonsense

Question 24

Suppose the size of a population of marmots is 300.According to genetic drift theory, what is the probability that a newly arisen neutral mutation will become fixed in this population?

A) 1/100
B) 1/300
C) 1/600
D) 1/1,000
E) 1/1,200

Question 25

Which change is a transition?

A) A change from A to G
B) A change from A to C
C) A change from T to G
D) A change from C to G
E) A change from C to G and back to C

Question 26

In a sequence of DNA taken from various species of snails, researchers have found that the rates of nonsynonymous substitutions and synonymous substitutions are roughly the same.What can we infer from this pattern?

A) Transversions are more common than transitions.
B) Most of the amino acid changes are neutral.
C) Strong purifying selection is acting on this gene.
D) Strong positive selection is acting on this gene.
E) This gene cannot be used as a molecular clock.

Question 27

Two species of plants that diverged 20 million years ago have accumulated an estimated 10 nucleotide differences in gene X.Species A has had an average population size of 3 million, while species B has had an average population size of 0.5 million.Both of these plants are annuals, with one generation per year.Assuming that the substitutions are all neutral, what is the estimated neutral mutation rate of gene X per million generations?

A) 0.25
B) 0.5
C) 1
D) 1.5
E) 3

Question 28

According to the neutral theory of molecular evolution, the fastest rate of fixation of neutral mutations by genetic drift should occur in a population of _______ individuals.

A) 200
B) 400
C) 1,000
D) 10,000
E) None of the above; the rates should be roughly the same for all.

Question 29

When a gene duplication occurs, _______ nucleotide substitutions are required for the evolution of a gene with a new function.

A) nonsynonymous
B) synonymous
C) silent
D) missense
E) nonsense

Question 30

Transcription factors are proteins that bind specific DNA sequences to regulate gene transcription.Some families of transcription factors bind zinc molecules to form structural motifs called zinc fingers, which facilitate binding to the DNA.Transcription factors that have the so-called classical zinc finger motif bind each zinc molecule via two cysteine and two histidine amino acids.When comparing the orthologs of these genes in closely related species, one would expect to find that the position and conservation of the cysteine and histidine amino acids in the compared sequences are

A) under neutral selective processes.
B) subject to genetic drift.
C) under positive selection.
D) under purifying selection.
E) highly variant.

Question 31

Two species of plants that diverged 20 million years ago have accumulated an estimated 10 nucleotide differences in gene X.Species A has had an average population size of 3 million, while species B has had an average population size of 0.5 million.Both of these plants are annuals, with one generation per year.Suppose that a sequence analysis of offspring and parents shows that the actual total mutation rate is 1.5 per million.Assuming that all mutations are either deleterious or neutral, approximately what fraction of the mutations are deleterious?

A) 1/6
B) 1/3
C) 1/2
D) 2/3
E) 5/6

Question 32

Suppose that under the conditions of an experiment, a particular virus has an expected substitution rate of 1 per 2,000 nucleotides per generation and a genome size of 10,000 nucleotides.The virus has one generation per hour.We would expect _______ substitutions between 9:00 am on Monday and 1:00 pm on Friday of the same week.

A) 5
B) 10
C) 100
D) 500
E) 1,000

Question 33

Nonsynonymous substitutions, synonymous substitutions, and pseudogenes have different rates of evolution, on average.Which order correctly represents those rates, from fastest to slowest?

A) Nonsynonymous substitutions, synonymous substitutions, pseudogenes
B) Nonsynonymous substitutions, pseudogenes, synonymous substitutions
C) Pseudogenes, nonsynonymous substitutions, synonymous substitutions
D) Pseudogenes, synonymous substitutions, nonsynonymous substitutions
E) Synonymous substitutions, pseudogenes, nonsynonymous substitutions

Question 34

According to the neutral theory of molecular evolution,

A) most alleles found in natural populations are neutral.
B) nearly all mutations have some effect on the organism.
C) the rate of fixation of neutral mutations is much faster in small populations than it is in large ones.
D) molecular clocks do not work.
E) neutral mutations accumulate through genetic drift.

Question 35

The mutation rate of a gene in a species of minnows is 2 per million nucleotides per generation.Only 25 percent of the mutations of this gene are selectively neutral; the rest are deleterious.What is the substitution rate of this gene (per million nucleotides per generation)?

A) 0.25
B) 0.5
C) 2
D) 4
E) This question cannot be answered without information about the size of the minnow population.

Question 36

The rate of fixation of neutral mutations, , is

A) independent of population size.
B) higher in small populations than in large populations.
C) higher in large populations than in small populations.
D) slower than the rate of fixation of deleterious mutations.
E) None of the above

Question 37

Which statement about nonsynonymous substitutions is true?

A) They always affect the protein's shape and charge.
B) They occasionally confer a selective advantage on the organism.
C) The frequency of their occurrence is roughly the same among different genes.
D) They are unlikely to be influenced by natural selection.
E) In most genes, they occur more frequently than synonymous substitutions do.

Question 38

Suppose that under the conditions of an experiment, a particular virus has an expected substitution rate of 1 per 2,000 nucleotides per generation and a genome size of 10,000 nucleotides.The virus has one generation per hour.Suppose you wanted to have populations of this virus to acquire approximately 100 substitutions.How long would you let the experiment run?

A) 10 hours
B) 20 hours
C) 50 hours (2 days)
D) 100 hours (4 days)
E) 200 hours (8 days)

Question 39

Suppose the size of a population of marmots is 300.Assuming that the neutral mutation rate for a particular gene is µ (mu), the number of new mutations at each gene in this population is _______ × µ.

A) 100
B) 200
C) 300
D) 500
E) 600

Question 40

Neutral substitutions accumulate between lineages primarily via

A) genetic drift.
B) purifying selection.
C) positive selection.
D) reversions.
E) transversions.

Question 41

In which group would you expect the greatest extent of lateral gene transfer to take place?

A) Bacteria
B) Plants
C) Invertebrates
D) Vertebrates
E) None of the above; lateral gene transfer is equally common across these groups.

Question 42

Refer to the figure. Members of the JAK family of nonreceptor kinases are involved in signaling pathways.The four paralogs JAK1, JAK2, JAK3, and TYK2 are found in humans, mice, chickens, and fish, as shown in the phylogenetic tree.According to this phylogenetic gene tree,

A) fruit fly hopscotch is more closely related to human TYK2 than human JAK1.
B) a duplication event led to the generation of the orthologs human JAK3 and mouse Jak3.
C) two duplication events in common ancestors to fish and humans created the orthologs JAK1, JAK2, JAK3, and TYK2.
D) both jak2a orthologs are pseudogenes.
E) JAK2 and JAK3 are examples of convergent evolution.

Question 43

Genes from many isolates of the influenza virus have been sequenced.In certain regions of the genome, nonsynonymous substitutions are much more frequent than synonymous substitutions.Which statement is the most likely explanation for this pattern?

A) A great deal of genetic drift is taking place.
B) Most of the amino acid changes are neutral.
C) Strong purifying selection is acting on these genes.
D) Strong positive selection is acting on these genes.
E) Mutations that change the amino acid are disadvantageous.

Question 44

Histones are proteins that play important roles in gene regulation.Between plants and animals, only two amino acid changes have occurred in the histone H4 protein, despite many synonymous changes.What can we infer from this observation?

A) A great deal of genetic drift is taking place.
B) Most of the amino acid changes are neutral.
C) Strong purifying selection is acting on these genes.
D) Strong positive selection is acting on these genes.
E) These genes are pseudogenes.

Question 45

Fossil, morphological, and molecular evidence shows that langurs and ruminants do not share a recent common ancestor.This is important with respect to lysozyme evolution, because it supports the hypothesis that the similar changes observed in the lysozyme sequence in both langurs and ruminants

A) are consistent with the neutral theory of evolution.
B) are homologous.
C) are the result of convergent evolution.
D) are the result of purifying selection.
E) follow a molecular clock.

Question 46

The best way to detect whether lateral gene transfer has occurred would be by

A) looking for orphaned LTRs in the genome.
B) looking for genes whose phylogenies differ from those of most other genes.
C) bioprospecting.
D) comparing the ratios of synonymous and nonsynonymous substitutions.
E) comparing the transition-to-transversion ratios.

Question 47

In which organism would you find the enzyme lysozyme?

A) Only in foregut fermenters
B) Only in the hoatzin
C) Only in foregut fermenters and the hoatzin
D) Only in mammals and a few closely related organisms
E) In nearly all animals

Question 48

Which statement provides the strongest evidence that most noncoding DNA is slightly deleterious?

A) Species with larger population sizes have more noncoding DNA.
B) Species with smaller population sizes have more noncoding DNA.
C) Species with smaller genomes lose DNA more slowly than those with larger genomes.
D) Species with larger genomes lose DNA more slowly than those with smaller genomes.
E) There is an inverse relationship between the total amount of DNA in the genome and the percentage of the DNA that is noncoding.

Question 49

In which organism or organisms would you find the enzyme lysozyme serving a defensive role against invading bacteria?

A) Only in foregut fermenters
B) Only in the hoatzin
C) Only in foregut fermenters and the hoatzin
D) Only in mammals and a few closely related organisms
E) In nearly all animals

Question 50

Which list ranks the organisms correctly in terms of the expected total amount of coding DNA in their genomes (from least coding DNA to most coding DNA)?

A) Bacterium, single-celled eukaryote, Drosophila, bird
B) Bacterium, Drosophila, bird, single-celled eukaryote
C) Single-celled eukaryote, bacterium, Drosophila, bird
D) Drosophila, single-celled eukaryote, bird, bacterium
E) Drosophila, bacterium, single-celled eukaryote, bird

Question 51

Which statement about about noncoding DNA is true?

A) Selection against the accumulation of noncoding DNA is more effective in species with small populations.
B) Noncoding sequences are thought to be slightly advantageous.
C) Large genomes can slow down the rates of a growing organism.
D) Noncoding DNA accumulates at the same rate in all species.
E) Noncoding DNA accumulates more quickly in species with large population sizes.

Question 52

Refer to the figure, which shows a phylogenetic tree of the engrailed gene family. Which gene is the same evolutionary distance from zebrafish En1b as is zebrafish En2b?

A) Zebrafish En1a
B) Chicken En1
C) Lamprey En
D) Chicken En2
E) Human En1

Question 53

Which statement about genome evolution is true?

A) Some salamanders have about 40 times as much DNA as humans do.
B) Humans have about 100 times as many genes as Drosophila.
C) Most eukaryotes have only a little noncoding DNA.
D) A larger genome always indicates greater complexity.
E) Most of the variation in genome size is due to the number of functional genes an organism has.

Question 54

Refer to the table, which shows the genome sizes, development times, and population sizes of four species of salamanders. These salamander data are consistent with

A) development rate hypothesis for genome size.
B) genome size being due to lateral gene transfer.
C) noncoding DNA being slightly advantageous.
D) noncoding DNA being slightly deleterious.
E) noncoding DNA having a regulatory effect.

Question 55

Which statement about genomes is true?

A) The genome sizes of all plants are smaller than those of all animals.
B) Humans have the largest genome size of all animals.
C) Most of the bacterial genome is noncoding.
D) The size of the genome is in direct proportion to the complexity of the organism.
E) The size of the genome varies widely among organisms.

Question 56

The human genome contains _______ protein-coding genes.

A) fewer than 15,000
B) between 15,000 and 30,000
C) between 30,000 and 50,000
D) between 50,000 and 100,000
E) more than 100,000

Question 57

The most likely reason that crickets (Laupala) have a larger genome size than fruit flies (Drosophila) is that crickets

A) lose noncoding DNA more slowly.
B) have a higher point mutation rate.
C) have a lower point mutation rate.
D) lack retrotransposons.
E) lack LTRs.

Question 58

Which genetic event is most like lateral gene transfer in its effects?

A) Gene duplication
B) Biased gene conversion
C) Unequal crossing over
D) Gene loss
E) Hybridization

Question 59

Which statement about the enzyme lysozyme is true?

A) A small group of closely related mammals has evolved a special form of lysozyme that functions in digestion.
B) The lysozymes found in the foregut fermenters resulted from convergent evolution.
C) Lysozyme could not have evolved a secondary function if it had been an enzyme with a vital primary function.
D) A high mutation rate in foregut fermenters allows their lysozymes to evolve rapidly.
E) Lysozymes first evolved as a defense against bacteria in the common ancestor of mammals.

Question 60

Refer to the figure. Members of the JAK family of nonreceptor kinases are involved in signaling pathways.The four paralogs JAK1, JAK2, JAK3, and TYK2 are found in humans, mice, chickens, and fish, as shown in the phylogenetic tree.According to this phylogenetic gene tree, which gene is a paralog to jak2b?

A) tyk2
B) jak1
C) jak2
D) jak2a
E) jak3

Question 61

Which scenario is not a likely occurrence after a gene duplication event?

A) One gene retains its function, while the other becomes a pseudogene.
B) Both genes retain their functions, but they are expressed in different patterns or tissues.
C) Both genes become pseudogenes.
D) One gene retains its function, while the other evolves to have a new function.
E) Both genes are deleted from the genome.

Question 62

A gene family has been accumulating nucleotide substitutions at a rate of 0.25 per million years.On average, there have been 80 substitutions between the common ancestor of this gene family and each of the various living forms of this gene.Based on these numbers, this gene family likely originated _______ million years ago.

A) 20
B) 80
C) 160
D) 200
E) 320

Question 63

To reconstruct the evolutionary history of species of birds, which type of genes should be considered in the analysis?

A) Orthologs
B) Paralogs
C) Pseudogenes
D) Genes involved in lateral gene transfer
E) Genes with no sequence changes

Question 64

The primary function of ribosomal RNA gene products is

A) to carry oxygen.
B) protein synthesis.
C) DNA preservation.
D) to act as transcription factors regulating development.
E) lateral gene transfer.

Question 65

Which statement about ribosomal RNA (rRNA) genes is false?

A) Nearly all multicellular animals have hundreds of copies of them, if not more.
B) Within a species, there is much variation, structurally and functionally, in the copies of the rRNA genes.
C) rRNA genes evolve through concerted evolution.
D) The multiple copies of rRNA genes within a species are very similar structurally.
E) The multiple copies of rRNA genes within a species are very similar functionally.

Question 66

The combined globin genes in a single individual are an example of

A) retrotransposons.
B) a gene family.
C) a gene tree.
D) synonymous genes.
E) a genome.

Question 67

Biased gene conversion is a mechanism of

A) unequal crossing over.
B) convergent evolution.
C) concerted evolution.
D) bioprospecting.
E) lateral gene transfer.

Question 68

The most likely way for proteins to acquire new functions is via

A) gene duplication.
B) retrotransposons.
C) bioprospecting.
D) biased gene conversion.
E) concerted evolution.

Question 69

Which outcome results from the misalignment of highly repeated genes?

A) Unequal crossing over
B) Biased gene conversion
C) Parallel substitutions
D) The production of paralogs
E) Transitions

Question 70

Refer to the figure, which shows a phylogenetic tree of the engrailed gene family. In the evolution timeline, which gene is the most recent paralog of zebrafish En2b?

A) Zebrafish En2a
B) Chicken En2
C) Lamprey En
D) Sea urchin En
E) Human En1

Question 71

Refer to the figure, which shows a phylogenetic tree of the engrailed gene family. Which gene is the most closely related ortholog of human En1?

A) Zebrafish En1a
B) Chicken En1
C) Lamprey En
D) Chicken En2
E) Mouse En1

Question 72

Which event is likely to affect the length of arrays of repetitive sequences?

A) Biased gene conversion
B) Unequal crossing over
C) Lateral gene transfer
D) Nonsynonymous nucleotide substitutions
E) Synonymous nucleotide substitutions

Question 73

Which statement is true?

A) All orthologs are paralogs.
B) All paralogs are orthologs.
C) All homologs are orthologs.
D) All orthologs are homologs.
E) No homologs are orthologs.

Question 74

Copies of genes in the same or different species that are related as the result of gene duplications are known as

A) analogs.
B) orthologs.
C) paralogs.
D) heterologs.
E) monologs.

Question 75

In order to estimate the age of the split between the globin gene clusters, scientists did which of the following?

A) Only examined the fossil record
B) Only constructed a molecular clock analysis
C) Examined the ratio of nonsynonymous to synonymous substitution rates
D) Both examined the fossil record and constructed a molecular clock analysis
E) Examined the ratio of functional genes to pseudogenes

Question 76

A biologist is examining the gene tree of a gene family of hormone receptor proteins.Which gene forms should she compare when focusing on changes in function due to gene duplication?

A) Orthologs
B) Paralogs
C) Analogs
D) Heterologs
E) Monologs

Question 77

Flying squirrels and flying lemurs do not actually fly but glide.They are able to glide because of the development of a patagium, a membrane that stretches from the forelimb to hindlimb on each side of the body.The independent development of this trait in two species that do not share a recent common ancestor with this trait indicates _______ evolution has occurred.

A) directed
B) convergent
C) divergent
D) genetic drift
E) synonymous

Question 78

The voltage-gated sodium channels of neurons are membrane proteins that play a fundamental role in the generation of action potentials.Blockage of their activity by toxins, such as tetrodoxin, causes paralysis.To determine which nucleotides confer resistance to tetrodoxin in puffer fish and other resistant animals, researchers can _______ the sodium channel genes of resistant and nonresistant animals.

A) map the missense mutations of
B) map the sequence deletions within
C) determine the rate of genetic drift within
D) quantify the number of gene duplications within
E) compare the rates of synonymous and nonsynonymous nucleotide substitutions within

Question 79

A gene family has been accumulating nucleotide substitutions at a rate of 0.25 per million years.On average, there have been 80 substitutions between the common ancestor of this gene family and each of the various living forms of this gene.How many substitutions are expected to have evolved between any pair of living forms of genes from this gene family?

A) 20
B) 40
C) 80
D) 160
E) 320

Question 80

Which statement about the globin family is false?

A) Hemoglobin has a higher affinity for oxygen than myoglobin does.
B) Myoglobin is the primary oxygen storage molecule in the muscles.
C) Hemoglobin and myoglobin have evolved to have somewhat different functions.
D) Hemoglobin has a tetrameric structure that allows it to carry more oxygen molecules than myoglobin does.
E) Myoglobin functions as a dimer.