Mastering Biology Assignment 5
directional selection
Sail-fin mollies (a small freshwater fish) prefer to mate with males that have long, colorful dorsal fins. The distribution of fin phenotypes in the males of this population would reflect _____.
artificial selection and directional selection
Southern farmers have produced a variety of corn that grows tall and bears large ears of corn despite the intense summer heat by which process?
a population's gene frequency
Which of these can change via natural selection?
Which of these is closest to the allele frequency in the founding population? A) 0.1 a, 0.9 A B) 0.2 a, 0.8 A C) 0.5 a, 0.5 A D) 0.8 a, 0.2 A E) 0.4 a, 0.6 A
a
Which of these is the smallest unit that natural selection can change? A) a speciesʹ gene frequency B) a populationʹs gene frequency C) an individualʹs genome D) an individualʹs genotype E) an individualʹs phenotype
b
Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true? A) Each bird evolved a deeper, stronger beak as the drought persisted. B) Each bird developed a deeper, stronger beak as the drought persisted. C) Each birdʹs survival was strongly influenced by the depth and strength of its beak as the drought persisted. D) Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation. E) The frequency of the strong-beak alleles increased in each bird as the drought persisted.
c
The Darwinian fitness of an individual is measured most directly by ? a. the number of mates it attracts. b. the number of "good genes" it possesses. c. the number of its offspring that survive to reproduce. d. its physical strength. e. how long it lives.
c.
Sexual dimorphism is most often a result of A) pansexual selection. B) stabilizing selection. C) intrasexual selection. D) intersexual selection. E) artificial selection.
d
HIV has 9 genes in its RNA genome. Every HIV particle contains two RNA molecules, each molecule containing all 9 genes. If, for some reason, the two RNA molecules within a single HIV particle do not have identical sequences, then which of these terms can be applied due to the existence of the non-identical regions? A) homozygous B) gene variability C) nucleotide variability D) average heterozygosity E) all except A
e
If the frequency of a particular allele that is present in a small, isolated population of alpine plants decreases due to a landslide that leaves an even smaller remnant of surviving plants bearing this allele, then what has occurred? A) a bottleneck B) genetic drift C) microevolution D) A and B only E) A, B, and C
e
If the original finches that had been blown over to the Galapagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galapagos, this would have been an example of A) genetic drift. B) bottleneck effect. C) founderʹs effect. D) all three of these E) both A and C
e
In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population? A) 0.36 B) 0.60 C) 0.64 D) 0.75 E) 0.80
e
A,B, & C
A forest fire kills most of the gopher tortoises in an area, and a population geneticist experimentally determines that the frequency of the recessive allele for shell thickness decreased from 0.67 before the fire to 0.21 after the fire. What has occurred?
0.60
A gene that is in Hardy-Weinberg equilibrium in the swallowtail butterfly population on St. George Island controls antennal length, whereby the long-antenna allele is completely dominant to the short-antenna allele. Of the 400 butterflies in this population, 256 butterflies have long antennae. What is the frequency of the recessive allele in this population?
0.50
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive phenotype, the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What is the estimated frequency of the dominant allele in the gene pool?
The two phenotypes are about equally adaptive under laboratory conditions.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive phenotype, the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait has not changed over time?
choices A,B, AND C
A pop'n. biologist obtains data indicating that the frequency of a particular recessive allele in a pop'n. previously in H/W equilibrium changed from 0.3 to 0.8. A possible explanation is _____.
Each insect's survival is strongly influenced by how resistant it is during a growing season.
A population of boll weevils (an insect that damages cotton crops) is subjected to aerial spraying of a pesticide repeatedly throughout the growing season. Which statement about pesticide resistance in boll weevils during the growing season is true?
sexual dimorphism was developing over time in these species
Adult male humans generally have deeper voices than do adult female humans, as the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females, and increasing larynx size in adult males, then _____.
a cline
An ecologist is able to correlate the darkness of leaves in a particular species of small plant with its exposure to sunlight: when plants grow on the forest floor under trees, their leaves are dark green; plants growing at the edge of the forest at the edge of the forest with intermediate levels of sunlight are moderately green; and plants growing in the open field next to the forest under maximum sunlight have leaves that are pale green.This observed difference in leaf color is an example of _____.
0.25
Assume that all possible "ABO" blood phenotypes are present in a certain population that is in Hardy-Weinberg equilibrium with respect to this class of blood-type alleles. The frequency of the "IA" allele is 0.3 and the frequency of the IB allele is 0.2. What is the frequency of individuals with Type O blood in the population?
0.24
Assume that all possible "ABO" blood phenotypes are present in a certain population that is in Hardy-Weinberg equilibrium with respect to this class of blood-type alleles. The frequency of the "IA" allele is 0.3 and the frequency of the IB allele is 0.2. What is the frequency of individuals with Type B blood in this population?
biological
Beetle pollinators of a particular plant are attracted to its flowers' bright orange color. The beetles not only pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, interbreeding is no longer possible between these two beetle variants. Based on this information, the two variants of beetles can be assigned to different species based on which species concept?
B (look at picture)
Blue light is that portion of the visible spectrum that penetrates the deepest into bodies of water. Ultraviolet (UV) light, though, can penetrate even deeper. A gene within a population of marine fish that inhabits depths from 500 m to 1,000 m has an allele for a photopigment that is sensitive to UV light, and another allele for a photopigment that is sensitive to blue light. Which graph below best depicts the predicted distribution of these alleles if the fish that carry these alleles prefer to locate themselves where they can see best?
populations
Gene flow is a concept best used to describe an exchange of alleles between _____.
closest anscestor is closer to bottom
If "x" indicates the location of fossils of two closely related species, then fossils of their most-recent common ancestor are most likely to occur in which stratum? _____
relative fitness
If genetic variation is truly "neutral," then it should have no effect on _____.
directional selection and adaptation
If the curve shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations, then which of these is (are) probably occurring?
The proportions of both types of homozygote should decrease & The population's average heterozygosity should increase.
In a hypothetical population's gene pool, an autosomal allele, which had previously been fixed, undergoes a mutation that introduces a new allele, one that is incompletely dominant to the original allele. Natural selection then causes stabilizing selection at this locus. Consequently, what should happen over the course of many generations?
mistakes in translation of structural genes.
In modern terminology, diversity is understood to be a result of genetic variation. Sources of variation for evolution include all of the following except _____.
A, B, and C
Lake Jackson is a 6.2-square mile lake on the northwest side of Tallahassee that drains every twenty-five years or so. Two sinkholes open up and the water in the lake drains into the Florida aquifer, or water table. The fish and other organisms in the lake obviously perish, except for those that survive in a small isolated pool. Remarkably, the lake gradually fills again over a period of several years as a result of rain and plant and animal populations rebound.A population geneticist experimentally determined that the large-mouth bass population in Tallahassee's Lake Jackson has a relatively high proportion of genes that are "fixed" in this population. As a result, this population would have relatively low ____.
0.70
Let's assume that the latest census of great blue herons that hang out by the FSU Reservation on Lake Bradford revealed a population of only 25 adult herons (so not likely to be in H/W equilibrium). For a gene that determines bill size, whereby the allele for stout bills is dominant to the allele for more slender bills, calculate the frequency of the recessive allele in this population if ten herons have slender bills and all other herons are heterozygous?
mate choice and intersexual selection
Sail-fin mollies (a small freshwater fish) prefer to mate with males that have long, colorful dorsal fins. Which of the following terms are appropriately applied to the situation described above?
The phenotype observed in the open field study plot arose from parental alleles causing dark leaves.
The ecologist plants seeds produced from the forest-floor plants in the open field and she plants seeds from the open-field plants in the forest floor. After a sufficient period of growth, she observes that plants in the open-field study plot have dark leaves and plants in the forest-floor study plot have pale-green leaves. How should she interpret these results?
the two forms interbreed in nature and their offspring survive and reproduce well
The myrtle warbler and Audubon's warbler were once listed as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?
the body design of snakes is analgous feature that evolved multiple times by convergent evolution
What best explains why all snakes have a similar body design even though they are not all descended from a common ancestor?
cannot be determined from this information
What is the frequency of the recessive allele for a particular gene in a population of frogs that is in Hardy-Weinberg equilibrium if the frequency of the heterozygote genotype is 0.42?
stabilizing selection
What is true of the trait whose frequency distribution in a large population appears above? It has probably undergone _____.
Genetic drift
What mechanism might account for the relatively high proportion of genes that are "fixed" in the Lake Jackson bass population?
0.50
What proportion of the population is probably heterozygous for this trait?
disruptive selection
Which describes an African butterfly species that exists with similar frequency in two strikingly different color patterns?
living 2 years and producing six offspring with one mate
Which of the following examples reflects the highest evolutionary fitness?
Silent mutations
Which of the following explains why comparing the DNA sequences of homologous genes and not the amino-acid sequences of homologus proteins is a more accurate way of determining the evolutionary relatedness of different species?
natural selection
Which of these evolutionary agents is most consistent at causing populations to become better suited to their environments over the course of generations?
All new alleles are the result of nucleotide variability.
Which statement about variation is true?
bottom of diagram is oldest
Which stratum (A-D) should contain the greatest proportion of extinct organisms? _____
Lamarck
Who believed that species could evolve by individuals striving to become better adapted to their environment generation after generation?
A trend toward the decrease in the size of plants on the slopes of mountains as altitudes increase is an example of A) a cline. B) a bottleneck. C) relative fitness. D) genetic drift. E) geographic variation.
a
If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about how many people will have attached earlobes when the planetʹs population reaches 10,000? A) 100 B) 400 C) 800 D) 1,000 E) 10,000
a
If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females, and increasing larynx size in adult males, then A) sexual dimorphism was developing over time in these species. B) intrasexual selection seems to have occurred. C) the ʺgood genesʺ hypothesis was refuted by these data. D) stabilizing selection was occurring in these species concerning larynx size. E) selection was acting more directly upon genotype than upon phenotype.
a
In modern terminology, diversity is understood to be a result of genetic variation. Sources of variation for evolution include all of the following except A) mistakes in translation of structural genes. B) mistakes in DNA replication. C) translocations and mistakes in meiosis. D) recombination at fertilization. E) recombination by crossing over in meiosis.
a
The outcome of the conflict between bacteria and bacteriophage at any point in time results from A) frequency-dependent selection. B) evolutionary imbalance. C) heterozygote advantage. D) neutral variation. E) genetic variation being preserved by diploidy.
a
The situation as described in the paragraph above should select most directly against males that A) are unable to distinguish food items that are red from those of other colors. B) are older, but still healthy. C) are capable of defending only moderately sized territories. D) have slightly lower levels of testosterone during breeding season than have other males. E) have no prior experience courting female house finches.
a
Which definition of evolution would have been most foreign to Charles Darwin during his lifetime? A) change in gene frequency in gene pools B) descent with modification C) the gradual change of a populationʹs heritable traits over generations D) populations becoming better adapted to their environments over the course of generations E) the appearance of new varieties and new species with the passage of time
a
Which of these makes determining the evolutionary relatedness of different species based on the amino acid sequence of homologous proteins generally less accurate than determinations of relatedness based on the nucleotide sequences of homologous genes? A) Silent mutations B) Gene duplications C) Translocation events that change gene sequences D) Crossing-over E) Independent assortment
a
Which of these variables is likely to undergo the largest change in value as the result of a mutation that introduces a brand-new allele into a populationʹs gene pool at a locus that had formerly been fixed? A) Average heterozygosity B) Nucleotide variability C) Geographic variability D) Average number of loci
a
Which population is most likely to be subject to the bottleneck effect? A) Population A. B) Population B. C) Population C. D) They are all the same. E) It is impossible to tell from the information given.
a
You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to A) cross your flies with flies from another lab. B) reduce the number of flies that you transfer at each generation. C) transfer only the largest flies. D) change the temperature at which you rear the flies. E) shock the flies with a brief treatment of heat or cold to make them more hardy.
a
Natural selection is most nearly the same as ? a. differential reproductive success. b. genetic drift. c. diploidy. d. non-random mating. e. gene flow.
a.
Sexual dimorphism is most often a result of ? a. intersexual selection. b. stabilizing selection. c. artificial selection. d. pansexual selection. e. intrasexual selection.
a.
Which of the following is a true statement concerning genetic variation? a. It must be present in a population before natural selection can act upon the population. b. It tends to be reduced by the processes involved when diploid organisms produce gametes. c. It is created by the direct action of natural selection. d. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity. e. It arises in response to changes in the environment.
a.
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.2. What is the frequency of individuals with Aa genotype? A) 0.20 B) 0.32 C) 0.42 D) 0.80 E) Genotype frequency cannot be determined from the information provided.
b
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.4. What is the percentage of the population that is homozygous for this allele? A) 4 B) 16 C) 32 D) 36 E) 40
b
In which population would it be least likely that an accident would significantly alter the frequency of the brown allele? A) Population A. B) Population B. C) Population C. D) They are all the same. E) It is impossible to tell from the information given.
b
Rank the following 1-base point mutations (from most likely to least likely) with respect to their likelihood of affecting the structure of the corresponding polypeptide: 1. insertion mutation deep within an intron 2. substitution mutation at the 3rd position of an exonic codon 3. substitution mutation at the 2nd position of an exonic codon 4. deletion mutation within the first exon of the gene A) 1, 2, 3, 4 B) 4, 3, 2, 1 C) 2, 1, 4, 3 D) 3, 1, 4, 2 E) 2, 3, 1, 4
b
What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time? A) The population is undergoing genetic drift. B) The two phenotypes are about equally adaptive under laboratory conditions. C) The genotype AA is lethal. D) There has been a high rate of mutation of allele A to allele a. E) There has been sexual selection favoring allele a.
b
Which of these is a statement that Darwin would have rejected? A) Environmental change plays a role in evolution. B) The smallest entity that can evolve is an individual organism. C) Individuals can acquire new characteristics as they respond to new environments or situations. D) Inherited variation in a population is a necessary precondition for natural selection to operate. E) Natural populations tend to produce more offspring than the environment can support.
b
Within the body of an HIV-infected individual who is being treated with a single NA, and whose HIV particles are currently vulnerable to this NA, which of these situations can increase the virusʹ relative fitness? 1. mutations resulting in RTs with decreased rates of nucleotide mismatch 2. mutations resulting in RTs with increased rates of nucleotide mismatch 3. mutations resulting in RTs that have proofreading capability A) 1 only B) 2 only C) 3 only D) 1 and 3 E) 2 and 3
b
Arrange the following from most general (i.e., most inclusive) to most specific (i.e., least inclusive): 1. Natural selection 2. Microevolution 3. Intrasexual selection 4. Evolution 5. Sexual selection A) 4, 1, 2, 3, 5 B) 4, 2, 1, 3, 5 C) 4, 2, 1, 5, 3 D) 1, 4, 2, 5, 3 E) 1, 2, 4, 5, 3
c
Each of the following has a better chance of influencing gene frequencies in small populations than in large populations, but which one most consistently requires a small population as a precondition for its occurrence? A) Mutation B) Non-random mating C) Genetic drift D) Natural selection E) Gene flow
c
Gene flow is a concept best used to describe an exchange between A) species. B) males and females. C) populations. D) individuals. E) chromosomes.
c
If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite different in the subsequent generations. This would be an example of A) diploidy. B) gene flow. C) genetic drift. D) disruptive selection. E) stabilizing selection.
c
If there are 4,000 children born to this generation, how many would be expected to have AB blood under the conditions of Hardy-Weinberg equilibrium? A) 100 B) 960 C) 1,920 D) 2,000 E) 2,400
c
If, on average, 46% of the loci in a speciesʹ gene pool are heterozygous, then the average homozygosity of the species should be A) 23% B) 46% C) 54% D) 92% E) There is not enough information to say
c
The DNA polymerases of all cellular organisms have proofreading capability. This capability tends to reduce the introduction of A) extra genes by gene duplication events. B) chromosomal translocation. C) genetic variation by mutations. D) proofreading capability into prokaryotes.
c
What is the estimated frequency of allele A in the gene pool? A) 0.05 B) 0.25 C) 0.50 D) 0.75 E) 1.00
c
What proportion of the population is probably heterozygous (Aa) for this trait? A) 0.05 B) 0.25 C) 0.50 D) 0.75 E) 1.00
c
Which is a true statement concerning genetic variation? A) It is created by the direct action of natural selection. B) It arises in response to changes in the environment. C) It must be present in a population before natural selection can act upon the population. D) It tends to be reduced by the processes involved when diploid organisms produce gametes. E) A population that has a higher average heterozygosity has less genetic variation than one with a larger average heterozygosity.
c
Which statement correctly describes the role of chance in evolution? a. Evolutionary change proceeds by an accumulation of changes that occur by chance. b. An allele that increases evolutionary fitness cannot be lost from a population by chance events. c. The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA
c.
About which of these did Darwin have a poor understanding? A) that individuals in a population exhibit a good deal of variation B) that much of the variation between individuals in a population is inherited C) the factors that cause individuals in populations to struggle for survival D) the sources of genetic variations among individuals E) how a beneficial trait becomes more common in a population over the course of generations
d
During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following is true of this situation? A) Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations. B) Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations. C) There should be directional selection for bright red feathers in males. D) All three of these. E) Only B and C.
d
HIVʹs genome of RNA includes code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR. 18) Which of these represents the treatment option that is most likely to avoid the production of drug -resistant HIV (assuming no drug interactions or side effects)? A) using a series of NAs, one at a time, and changed about once a week B) using a single PI, but slowly increasing the dosage over the course of a week C) using high doses of NA and a PI at the same time for a period not to exceed 1 day D) using moderate doses of NA and of two different PIʹs at the same time for several months
d
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the percentage of the population that is heterozygous for this allele? A) 90 B) 81 C) 49 D) 18 E) 10
d
In which population is the frequency of the allele for brown feathers highest? A) Population A. B) Population B. C) Population C. D) They are all the same. E) It is impossible to tell from the information given.
d
Over the course of evolutionary time, what should occur? A) Methylated DNA should become fixed in the gene pools of bacterial species. B) Nonmethylated DNA should become fixed in the gene pools of bacteriophages. C) Methylated DNA should become fixed in the gene pools of bacteriophages. D) Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time. E) Both A and B are correct.
d
Sponges are known to contain a single Hox gene. Most invertebrates have a cluster of 10 similar Hox genes, all located on the same chromosome. Most vertebrates have four such clusters of Hox genes, located on four non-homologous chromosomes. The process responsible for the change in number of Hox genes from sponges to invertebrates was most likely __________, whereas a different process that could have potentially contributed to the clusterʹs presence on more than one chromosome was __________. I. binary fission II. translation III. gene duplication IV. non-disjunction V. transcription A) I, II B) II, III C) II, V D) III, IV E) III, V
d
Which of the following terms are appropriately applied to the situation described in the previous question? A) Sexual selection B) Mate choice C) Intersexual selection D) All three of these E) Only B and C
d
Which of these evolutionary agents is most consistent at causing populations to become better suited to their environments over the course of generations? A) Mutation B) Non-random mating C) Gene flow D) Natural selection E) Genetic drift
d
Which statement about variation is true? A) All phenotypic variation is the result of genotypic variation. B) All genetic variation produces phenotypic variation. C) All nucleotide variability results in neutral variation. D) All new alleles are the result of nucleotide variability. E) All geographic variation results from the existence of clines.
d
Cattle breeders have improved the quality of meat over the years by which process? a. artificial selection b. directional selection c. stabilizing selection d. artificial selection and directional selection e. artificial selection and stabilizing selection
d.
If two genes from one RNA molecule become detached and then, as a unit, get attached to one end of the other RNA molecule within a single HIV particle, which of these is true? A) There are now fewer genes within the viral particle. B) There are now more genes within the viral particle. C) A point substitution mutation has occurred in the retroviral genome. D) The retroviral equivalent of crossing-over has occurred, no doubt resulting in a heightened positive effect. E) One of the RNA molecules has experienced gene duplication as the result of translocation.
e
In a hypothetical populationʹs gene pool, an autosomal gene, which had previously been fixed, undergoes a mutation that introduces a new allele, one inherited according to incomplete dominance. Natural selection then causes stabilizing selection at this locus. Consequently, what should happen over the course of many generations? A) The proportions of both types of homozygote should decrease. B) The proportion of the population that is heterozygous at this locus should remain constant. C) The populationʹs average heterozygosity should increase. D) Both (A)and (B) E) Both (A)and (C)
e
Natural selection is most nearly the same as A) diploidy. B) gene flow. C) genetic drift. D) non-random mating. E) differential reproductive success.
e
Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing A) non-random mating. B) geographic isolation. C) genetic drift. D) mutations. E) gene flow.
e
The higher the proportion of loci that are ʺfixedʺ in a population, the lower is that populationʹs A) nucleotide variability. B) genetic polyploidy. C) average heterozygosity. D) A, B, and C E) A and C only
e
What is the frequency of the B allele? A) 0.001 B) 0.002 C) 0.100 D) 0.400 E) 0.600
e
Which of these is the smallest unit upon which natural selection directly acts? A) a speciesʹ gene frequency B) a populationʹs gene frequency C) an individualʹs genome D) an individualʹs genotype E) an individualʹs phenotype
e
You sample a population of butterflies and find that 42% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population? A) 0.09 B) 0.30 C) 0.49 D) 0.70 E) Allele frequency cannot be determined from this information.
e
Each of the following has a better chance of influencing gene frequencies in small populations than in large populations, but which one most consistently requires a small population as a precondition for its occurrence? a. Non-random mating b. Gene flow c. Mutation d. Natural selection e. Genetic drift
e.
The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. The outcome of the conflict between bacteria and bacteriophage at any point in time results from? a. neutral variation. b. genetic variation being preserved by diploidy. c. evolutionary imbalance. d. heterozygote advantage. e. frequency-dependent selection.
e.
