Deck 20: Evolution of Genes and Traits

Question 1

Which of these principles of evolution,as described by Darwin's theory,is correctly matched with its role in evolution?

A)Principle of variation: Offspring must resemble their parents more than they resemble unrelated individuals.
B)Principle of selection: Variation in morphology,physiology,and behavior must be present in a population for selection to occur.
C)Principle of variation: Variation in morphology,physiology,and behavior must be present in a population for selection to occur.
D)Principle of heredity: Some genotypes of a population should be more successful at surviving and reproducing than other genotypes in a given environment.
E)None of the answer options are correct.

Answer 1

C

Question 2

When considering the rate of nucleotide divergence for a particular gene over time,which of the following has been observed to be true?

A)Nonsynonymous mutations will become established less frequently.
B)Adenine nucleotides are more readily mutated than other nucleotides.
C)Synonymous mutations will become established less frequently.
D)Nucleotide changes over time are impossible to measure.
E)Only noncoding sequences display change.

Answer 2

A

Question 3

Balanced polymorphism is illustrated by:

A)a situation where the selective pressure enhances the frequency of heterozygotes over homozygotes.
B)a situation where the selective pressure enhances the frequency of homozygotes over heterozygotes.
C)only situations where disease impacts allele frequency.
D)situations where allelic homozygosity is impossible.
E)All of the answer options are correct.

Answer 3

A

Question 4

Plasmodium falciparum is a parasitic protist that can be carried among host organisms by a mosquito.Infection generates anemia via a process of:

A)infecting the bone marrow of its hosts.
B)causing uncontrolled bleeding from tissues.
C)invading red blood cells and dividing within them.
D)mosquito-based feeding upon the blood during transmission.
E)anemia is not a symptom of Plasmodium infection.

Question 5

Tony Allison examined the allele frequency of hemoglobin (HbA,or HbS)in populations of Kenyon tribes.A surprising result of this study was that:

A)the HbS and HbA alleles were evenly distributed among Kenyan tribes.
B)the HbS alleles appeared more frequently in men than in women.
C)tribes living in arid or highland regions had high frequencies of HbS alleles.
D)tribes living near Lake Victoria had a low frequency of HbS alleles.
E)tribes living in arid or highland regions had low frequencies of HbS alleles.

Question 6

Which of the following are requirements for evolution by natural selection?
I environmental change
II differential survival and reproduction
III heritability of phenotypic variation
IV variation in phenotype
V sexual reproduction

A)II,III,V
B)II,III,IV
C)I,II,IV
D)III,IV,V
E)II,IV,V

Question 7

When considering synonymous and nonsynonymous mutations within a population,which of the following is TRUE?

A)Nonsynonymous mutations will often be removed by purifying selection.
B)Synonymous mutations will often be removed by purifying selection.
C)The two types of mutations are not distinguished by purifying selection.
D)Only nonsynonymous mutations are known to occur.
E)Only synonymous mutations are known to occur.

Question 8

Which researcher proposed that change was caused by the environment acting directly on an organism,and that those changes acquired in an organism's lifetime were passed on to its offspring?

A)Gould
B)Darwin
C)Wallace
D)Lamarck
E)Allison

Question 9

The gene for which of the following proteins is likely to have the higher neutral rate of mutation?

A)cytochrome c
B)alpha subunit of hemoglobin
C)beta subunit of hemoglobin
D)fibrinopeptides
E)actin

Question 10

What term could be used to describe the type of selection occurring with the sickle-cell and normal hemoglobin alleles among areas where malaria is present?

A)directional selection
B)balancing selection
C)stabilizing selection
D)genetic drift
E)inbreeding depression

Question 11

The molecular basis of sickle cell hemoglobin is:

A)a frameshift mutation.
B)a single nucleotide substitution.
C)a translocation event.
D)a virus induced inversion.
E)exposure to a chemical mutagen.

Question 12

The neutral theory of evolution proposed that most genetic mutations are functionally neutral or nearly neutral.Neutral mutations would be fixed in a population by:

A)natural selection.
B)random genetic drift.
C)balancing selection.
D)asexual reproduction.
E)the invariance of DNA.

Question 13

Which of the following processes will increase genetic variation within populations?

A)incompatible selection
B)mutation
C)directional selection
D)asexual reproduction
E)genetic drift

Question 14

In human populations,the "AS" allele arose from:

A)the insertion of a mutagenic transposon into the Hb gene.
B)one individual located in central Africa.
C)five independent events,in separate populations.
D)a frameshift mutation in the Hb gene.
E)a plasmodium-induced change in DNA sequence.

Question 15

Which of the following is/are NOT a principle of Darwinian evolution?

A)There is variation in morphology,physiology,and behavior among individuals in a population.
B)Offspring resemble their parents more closely than unrelated individuals.
C)In any given environment,some individuals are more successful at surviving and reproducing than others.
D)Darwinian evolution fully describes where all living things come from.
E)All of the answer options are correct.

Question 16

Why don't we find different human populations with different fixed alleles at a certain locus?

A)Inbreeding is high.
B)Migration between populations is high.
C)The mutation rate is lower than the critical value.
D)Population sizes are too large.
E)Allelic variation is low.

Question 17

When considering hemoglobin alleles,scientists concluded that the proportions of the two alleles within a population was strongly affected by:

A)the severity of malaria.
B)the atmospheric pressure of O₂.
C)the rate of elimination of harmful HbS alleles.
D)the nutritional intake of each individual.
E)the severity of malaria and the rate of elimination of harmful HbS alleles.

Question 18

The fitness advantage of the "AS" allelic combination can be calculated by:

A)measuring O₂-carrying capacity in the blood of "AS" individuals.
B)comparing the actual frequency of "AS" to the frequency predicted by the Hardy-Weinberg equation.
C)measuring the frequency of "AS" in the population.
D)infecting the blood of "AS" individuals with the parasite.
E)measuring the frequency of "AA" and subtracting that value from the frequency of "AS."

Question 19

Which of the following reduce heterozygosity?

A)migration
B)directional selection
C)large population size
D)balancing selection
E)mutation

Question 20

Which of the following processes will increase variation between populations?

A)earthquakes
B)mutation
C)migration
D)balancing selection
E)inbreeding

Question 21

In southwestern Arizona,the melanocortin 1 receptor mutation-bearing mice (dark hair)are commonly found in:

A)rocky lava outcrops.
B)stream beds.
C)sandy desert regions.
D)mixed rodent populations.
E)high mountain regions.

Question 22

Assume that the following amino acid sequences were obtained for a highly conserved gene,gene X,in eukaryotes.Using this information,determine the most probable ancestral amino acid sequence.

Question 23

What is meant by the phrase,"The force of selection is myopic."?

Question 24

Define the molecular clock.

Question 25

Some of the most striking and best understood examples of morphological divergence are found in:

A)populations of antibiotic resistant bacteria.
B)virology.
C)animal body-color patterns.
D)mouse eye-color mutants.
E)blood-type examples in mammals.

Question 26

How will pleiotropy affect selection at particular loci?

Question 27

Organophosphate resistance in the sheep blowfly (Luciliacuprina)is an example of:

A)the toxicity of insecticides.
B)the generation of neutral mutations over time.
C)a lethal frameshift mutation.
D)cumulative selection.
E)evolutionary selection of a single amino acid change in a protein.

Question 28

Describe how a population can shift adaptive peaks.Be clear about what mechanisms can accomplish this transition.

Question 29

A strawberry breeder wants to increase the yield of strawberry plants.To do so,he selects the two highest-yielding plants from a segregating population and uses them as parents that he hopes will produce higher yielding offspring.How would you use Darwin's evolutionary theory to explain the following results?
a)The breeder was able to obtain a better-yielding offspring.
b)The breeder was unable to obtain a better-yielding offspring.

Question 30

An adaptive walk of beta-lactamase in response to selective pressure exerted by cefotaxime likely involved:

A)the random generation of five changes that provide microbial resistance to the antibiotic.
B)sequential changes in single amino acids that each provided an incremental level of resistance to the antibiotic.
C)increased genetic change induced by selective pressure exerted by the antibiotic.
D)one clear beneficial change and several non-impactful changes in the gene.
E)major shifts in the metabolic pathways in the microbe under selection.

Question 31

In E.coli,the mutation of beta-lactamase in response to cefotaxime exposure involved five changes in the gene sequence,which can be accomplished through __________ different orderings.

A)16
B)32
C)64
D)120
E)240

Question 32

The rate of change is not identical for all genes.The following graph shows the rate of change of four hypothetical human proteins (A-D).Use this graph to answer the following questions.

a)Which of the proteins is changing at the fastest rate?
b)Which protein is most conserved?
c)Which evolutionary force (drift,selection,or migration)plays the biggest role in causing the observed difference in the rate of change between proteins A-D?
d)If you do Southern hybridization to determine if the genes encoding each of these human proteins (A-D)also exist in rice,which would give the strongest hybridization signal? Justify your answer.
e)If you were going to use one of the proteins to build a phylogenetic tree of various mammalian species (which diverged during the last 50 million years),which protein sequence would be most useful? Justify your answer.
f)If you were going to use one of the proteins to build a phylogenetic tree of various plant species (which diverged during the past 500 million years),which protein sequence would be most useful? Justify your answer.
g)If you were going to use one of the proteins to build a phylogenetic tree of a mixture of plant and animal species (which diverged 1200 million years ago),which protein sequence would be most useful? Justify your answer.

Question 33

Darwin's theory of evolution was developed around three central principles: the principle of variation,the principle of heredity,and the principle of selection.Define each of these principles,and explain their role in evolution.

Question 34

Inherited blindness in some cavefish arose through:

A)an individual mutant fish that displayed reproductive success.
B)atrophy of the eye when unused in darkness.
C)viral infection of the optic nerve.
D)a defect in gene splicing.
E)separate incidences of inactivating mutation in the Oca2 gene.

Question 35

In fruit flies,mutations in cis-acting regulatory sequences are associated with:

A)abnormal functioning of operator sequences.
B)body form/color variations.
C)changes in fruit fly behavior.
D)changes in reproductive fitness.
E)an alteration of DNA replication.

Question 36

An excess of nonsynonymous fixed mutations between species is likely due to:

A)natural selection.
B)random genetic drift.
C)a catastrophic event.
D)inbreeding.
E)immigration.

Question 37

Wichman and colleagues examined adaptive walks using:

A)antibiotic selection on bacteriophage populations.
B)bacteriophage infection of mutation-bearing bacteria.
C)a bacteriophage and two different host cell types.
D)mutagenic compounds delivered to rapidly dividing phage virions.
E)None of the answer options are correct.

Question 38

An orchid breeder is interested in increasing the number of stems and the length of stems that can be produced by an orchid plant.She finds a segregating population that contains a wide range of both stem number (ranging from 2 to15 stems per plant)and stem length (ranging from 2 to 7 inches in length).She selected plants from this population that either had the most stems per plant or the longest stems per plant (shown as filled regions in the diagrams below).She then interbred the plants with the most stems (or the longest stems)and grew the resulting populations of orchids.Following an additional round of selection and breeding,the breeder drew graphs to look at the distribution of plants in each generation.Shown below are graphs representing the distribution of plants in each generation in terms of stem number and stem length (in inches).For each trait,determine whether or not the trait is heritable.Justify your answers.

Question 39

The melanocortin 1 receptor protein displays four amino acid substitutions between dark- and light-colored populations of pocket mice.In dark mice,these unique amino acids cause the receptor to:

A)fold inappropriately in the cell membrane.
B)incorrectly identify ligand.
C)be non-functional in regulating gene expression.
D)be internalized and degraded.
E)be constitutively active.

Question 40

Can behaviors be the product of selection,even when their heritability is either very low or zero? Justify your answer.

Question 41

Three types of selection are "directional selection," "balancing selection," and "selection against heterozygotes."
a)Shown below are three graphs (A-C).Each graph represents a different type of selection.In each case,certain individuals are being selected against (represented by the striped regions).For each graph,write the name of the type of selection that is depicted.
A)

B)

C)


b)Described below are three examples of selection.For each example,write the name of the type of selection being described.

i)A maize breeder selects for increased ear size in maize in order to increase yield.

ii)Susceptibility to malaria and sickle-cell anemia is controlled by the same gene.The Hb^A allele provides resistance to sickle-cell anemia but not to malaria (thus,individuals who have the genotype Hb^AHb^A die from malaria),and the Hb^S allele provides resistance to malaria but not to sickle-cell anemia (thus,individuals with the genotype Hb^SHb^S die from sickle-cell anemia).Hb^AHb^S individuals are resistant to both diseases.

iii)Lower-yielding beans are resistant to anthracnose,whereas higher-yielding varieties are susceptible to the disease.Anthracnose is present only in certain areas of the region.So,breeders want to select higher- and lower-yielding plants to fulfill different breeding goals.

Question 42

Suppose that a population composed of 100 individuals existed on an island in the Caribbean Sea.Two different alleles of the A gene were present in this population (a¹ and a²)at equal frequency.The following events occurred to this unlucky population.Determine what evolutionary force (mutation,migration,drift,or selection)is represented by each event.In addition,tell the effect of each event on the genetic composition of the population.
a)A devastating fire caused the death of 10 individuals.
b)A disease swept through the island and killed 13 individuals.The a¹ confers resistance to the disease.
c)A disease swept through the island killing 13 individuals.Neither a¹ nor a² confers resistance to the disease.
d)A ship containing individuals from a different island containing a¹,a²,and a³ alleles landed at the island.
e)The president (whose genotype is a¹a¹)declared that all a¹ individuals had more rights than a² individuals.All a² individuals moved to another island.
f)An individual who was working in a cave stumbled upon a new rock and decided to put it in his pants pockets to show his wife.Some of their babies had an a⁴.

Question 43

A key step in the generation of new genes appears to be increases in the number of copies of existing genes.Define the mechanisms that can increase the copy number of a particular gene.

Question 44

There are several programs that allow researchers to search DNA databases with a newly acquired DNA sequence.One program,BLAST (www.ncbi.nlm.nih.gov/BLAST/),allows researchers to compare their sequence with all publicly available sequences.The search engine returns a list of similar sequences,with an estimate of similarity score (the greater the similarity between two sequences,the larger the score),and reveals the function of these similar sequences (if known).Suppose that you have just cloned and sequenced a gene from a gorilla,but you do not know what it does in a cell.You do a BLAST search using your gorilla sequence.Some of the output from the search is shown below:

a)What is the likely function of the gorilla gene?
b)Why does the output include sequences from species other than gorilla?
c)Why are some sequences more similar than others?

Question 45

What will determine the rate of a molecular clock for a gene that codes for a functional protein?

Question 46

Most genetic variation for many human loci lies within local populations rather than between populations or races.What does this observation tell you about human genetic evolution?

Question 47

In what way can synonymous mutations still have a selective component?

Question 48

Suppose that you have cloned and sequenced a gene that controls fruit size in strawberry.However,you do not know the function of the gene.
a)Describe how you could determine if this gene is also present in Arabidopsis (which has been fully sequenced).
b)Describe how you could determine if the gene is present in day lily (which has not been fully sequenced).
c)How could you determine a putative function for this gene?

Question 49

Describe the relationship between overall DNA change and functional change.

Question 50

Following a gene duplication event,the additional copy of the gene is identical to the original copy.
a)Does the duplication event,by itself,create a novel function?
b)How does a gene duplication event promote the creation of a gene with a novel function?

Question 51

Mutations within the Oca2 gene are associated with albinism and blindness in cavefish,while mutations in MC1R have been associated with increased pigmentation in the hairs of some pocket mice.With regard to protein function,compare the mutations generating each alteration of phenotype.

Question 52

Why do you expect different rates of evolution for synonymous versus nonsynonymous nucleotide substitutions?

Question 53

Based on your knowledge of the endogenous causes of mutation,what features of an organism's phenotype or ecology should affect the molecular clock?

Question 54

In a reforestation project,a fast-growing pine tree (fast-growing due to a dominant A allele)was selfed,and the resulting seed were planted on two islands (X and Y).One year after planting,there was a severe termite attack on Island X.The termites,which killed all slow-growing trees,destroyed 25% of the trees on the island.A severe cyclone struck Island Y and randomly killed 25% of its trees.Justify all answers.

a)With the information provided above,can you suggest the genotype of the original fast-growing tree that was selfed to obtain seed?
b)What evolutionary force is at work on Island X?
c)What evolutionary force is at work in Island Y?
d)Following the termite and cyclone attacks,which of the pine populations (X or Y)will have the most genetic variation?
e)Suppose that the cyclone that struck Island Y did so early in the year,before the emergence of the slow-growing trees.In this case,what evolutionary force is at work on Island Y?