Question 1

Consider a population with two loci (A, B), each with two alleles (A, a; B, b). What are the allele frequencies in this population if the haplotype frequencies are AB = 0.35, Ab = 0.15, aB = 0.35, ab = 0.15?
A) A =0.5, a = 0.5, B = 0.7, b = 0.3
B) A =0.7, a = 0.3, B =0.5, b =0.5
C) A = 0.6, a = 0.4, B = 0.7, b = 0.3
D) A = 0.5, a = 0.5, B = 0.6, b= 0.4

Accepted Answer

To find the allele frequencies, sum the haplotype frequencies for each allele. For A: 0.35 (AB) + 0.15 (Ab) = 0.5. For a: 0.35 (aB) + 0.15 (ab) = 0.5. For B: 0.35 (AB) + 0.35 (aB) = 0.7. For b: 0.15 (Ab) + 0.15 (ab) = 0.3.

Question 2

The figure shown demonstrates the genotypic adaptive landscape for bacteria growing in media without antibiotics. The height of the bars associated with a genotype indicates the fitness of that genotype. The R allele confers resistance to antibiotics, and the C allele compensates for the loss of fitness that the R allele confers in the absence of antibiotics. The rc haplotype lacks both compensation and resistance. Based on this landscape, why are resistance and compensation unlikely to be lost even in the absence of antibiotics? 
A) A lack of mutation will prevent the haplotypes from changing.
B) Epistasis will maintain haplotype frequencies.
C) Haplotype frequencies do not change in Hardy-Weinberg populations.
D) RC populations are stuck on a local maximum.

Accepted Answer

The figure shows that the RC haplotype has the lowest fitness, while the RC haplotype with compensation (CC) and the resistant haplotype (RR) have significantly higher fitness. The height of the bars indicates that these genotypes are stuck on a local maximum, meaning that any mutation that reduces the fitness of these haplotypes will be selected against, preventing these traits from being lost even in the absence of antibiotics. This phenomenon is known as stabilizing selection, which maintains the status quo of a population.

Question 3

The statistical association of alleles at different loci is referred to as
A) linkage disequilibrium.
B) Hardy-Weinberg equilibrium.
C) epistasis.
D) linkage equilibrium.

Accepted Answer

Linkage disequilibrium refers to the statistical association of alleles at different loci, where the occurrence of one allele at a particular locus is more often associated with the occurrence of a particular allele at another locus than would be expected by chance. Hardy-Weinberg equilibrium refers to the theoretical distribution of allele and genotype frequencies in an ideal, non-evolving population. Epistasis refers to the interaction between different genes, where the expression of one gene can affect the expression of another. Linkage equilibrium refers to the absence of linkage disequilibrium, where the occurrence of alleles at one locus is independent of their occurrence at another locus.

Question 4

Which of the following is most likely to break up linkage disequilibrium?
A) drift
B) selection
C) mutation
D) recombination

Accepted Answer

Recombination breaks up linkage disequilibrium. Recombination breaks up the physical association between alleles at different loci, which breaks up the linkage disequilibrium between them. Drift, selection, and mutation do not necessarily break up linkage disequilibrium.

Question 5

Hardy-Weinberg at two loci The figure demonstrates Hardy-Weinberg frequencies at two loci. Which term represents the expected offspring haplotype frequencies for a cross between parents with aB and aB gametes? A) uv B) u² C) tu D) t²

Accepted Answer

The answer of Hardy-Weinberg at two loci  The figure...

Question 6

The rediscovery of Mendelian inheritance caused increased scrutiny of Charles Darwin's theory of natural selection because of an apparent conflict in the two concepts. This conflict was based on the observation that Darwin focused on continuous traits, whereas Mendelian genetics deals with
A) discrete characters.
B) alleles.
C) garden pea plants.
D) genotypes.

Accepted Answer

Mendelian genetics deals with the inheritance of discrete characters, which are determined by specific genes with distinct phenotypic outcomes. This is in contrast to continuous traits, which are influenced by multiple genes and environmental factors and show a range of intermediate phenotypes. Darwin's theory of natural selection was based on the gradual accumulation of small variations within populations, which would eventually lead to the emergence of new species. The rediscovery of Mendelian inheritance challenged this idea by showing that certain traits were determined by discrete genetic factors that could be passed down from one generation to the next without blending or averaging out. However, later studies showed that natural selection could still operate on discrete traits, as long as there was variation within a population and some alleles had a selective advantage over others. Thus, the apparent conflict between Mendelian genetics and Darwin's theory of natural selection was resolved by integrating the two concepts into the modern synthesis of evolutionary biology.

Question 7

What is one reason why antibiotic resistance does not always disappear as quickly as one might expect after large-scale antibiotic use is ended?
A) Compensatory mutations arise at other loci in resistant bacterial strains, which eliminate fitness costs associated with the resistant phenotype.
B) Horizontal gene transfer occurs from other resistant bacterial strains.
C) Alleles for antibiotic resistance confer no fitness costs.
D) Alleles for antibiotic resistance confer no fitness benefits.

Accepted Answer

Compensatory mutations at other loci can eliminate the fitness costs associated with antibiotic resistance, allowing the resistant bacteria to persist even after antibiotic use has been discontinued. This can lead to the continued spread of antibiotic resistance.

Question 8

Narrow-sense heritability is defined as the ________ genetic variation divided by the ________ variation.
A) total; total phenotypic
B) additive; total phenotypic
C) dominance; total phenotypic
D) additive; total dominance

Accepted Answer

Narrow-sense heritability (h²) is defined as the proportion of phenotypic variation in a trait that is due to additive genetic variation. Therefore, it is calculated by dividing the additive genetic variation by the total phenotypic variation. Option A is incorrect because total genetic variation includes both additive and non-additive genetic components. Option C is incorrect because dominance variation is a non-additive genetic component and is not used in calculating narrow-sense heritability. Option D is incorrect because dominance variation is not included in calculating narrow-sense heritability.

Question 9

What is the largest possible value that linkage disequilibrium can reach if all allele frequencies are 0.5?
A) 0.25
B) 0.5
C) 0.75
D) 1

Accepted Answer

Linkage disequilibrium (D) is maximized when one of the haplotypes (combinations of alleles at different loci) is absent, leading to D = pA pB - pAB = (0.5)(0.5) - 0 = 0.25, where pA and pB are the allele frequencies (both 0.5 in this case) and pAB is the frequency of the haplotype combining both alleles A and B (0 in the case of maximum disequilibrium).

Question 10

What two major concepts in biology were unified in the middle of the twentieth century?
A) natural selection and genetic drift
B) discontinuous and continuous variation
C) mutation and migration
D) natural selection and Mendelian genetics

Accepted Answer

In the middle of the twentieth century, natural selection and Mendelian genetics were unified through the work of scientists such as Theodosius Dobzhansky, Ernst Mayr, and J.B.S. Haldane. This led to the development of the modern synthesis, which combined Darwin's theory of natural selection with Mendelian genetics to provide a comprehensive explanation of how evolution works.

Question 11

Consider two loci located close together on a single chromosome. These loci
A) carry alleles that will never segregate together.
B) are physically linked.
C) are in linkage equilibrium.
D) are likely to be broken up during recombination.

Accepted Answer

Loci located close together on a single chromosome are physically linked. This means that they tend to be inherited together rather than independently, as they are less likely to be broken up during recombination. Therefore, option B is the correct choice. Option A is incorrect because alleles located close together on the same chromosome tend to be inherited together. Option C is incorrect because linkage equilibrium refers to the independent assortment of loci that are not physically linked. Option D is incorrect because loci that are physically linked are less likely to be broken up during recombination.

Question 12

A haplotype is
A) all of the alleles at a single locus.
B) a product of epistasis.
C) a set of alleles at different loci along a chromosome.
D) all of the alleles in a population.

Accepted Answer

A haplotype is a set of alleles at different loci along a chromosome. It is the combination of alleles that are inherited together from one parent.

Question 13

Genotypic adaptive landscapes may better represent true adaptive landscapes than phenotypic adaptive landscapes when
A) single mutations can have a large effect on the phenotype.
B) phenotypic landscapes are hard to mathematically model.
C) phenotypic landscapes do not account for drift.
D) genotypic landscapes are easier to visualize.

Accepted Answer

When single mutations have large effects on the phenotype, it may be easier to predict the adaptive landscape based on genotypic rather than phenotypic data. This is because small changes in the genotype can have large effects on the resulting phenotype, and it may be difficult to accurately model these effects using only phenotypic data.

Question 14

In quantitative genetic terms, a phenotypic value can be expressed as
A) dominant or recessive.
B) epistasis and pleiotropy.
C) genotypic value and environmental deviation.
D) selection differential and selection response.

Accepted Answer

A phenotypic value is a reflection of both the genetic and environmental factors that contribute to a phenotype. The genotypic value represents the genetic contribution, while the environmental deviation represents the non-genetic contribution. Therefore, choice C is the best answer, as it specifically addresses the two components that make up a phenotypic value. Choices A, B, and D are all terms related to classical Mendelian genetics, and do not directly address the concept of phenotypic value.

Question 15

Which of the following occurs when there is so much Mendelian variation within a population that not all possible genotypes could be represented in any given generation?
A) epistasis
B) natural selection
C) latent variation
D) pleiotropy

Accepted Answer

The answer of Which of the following occurs when there...

Question 16

Assuming the value of linkage disequilibrium (D) is positive, recombination will generate
A) more repulsion pairs.
B) more coupling pairs.
C) no change, since recombination does not change expected haplotype frequencies.
D) an increase in the value of D.

Accepted Answer

When the value of linkage disequilibrium (D) is positive, recombination tends to break down the association between alleles, leading to more coupling pairs. This is because recombination reduces the non-random association between alleles at different loci, thereby decreasing D and increasing the generation of coupling pairs as opposed to repulsion pairs.

Question 17

Which of the following processes that can create linkage disequilibrium is illustrated in the figure? 
A) drift
B) selection
C) mutation
D) migration

Accepted Answer

The answer of Which of the following processes that can...

Question 18

If the value of linkage disequilibrium (D) is equal to -0.25, one can infer that the alleles are
A) in repulsion.
B) in coupling.
C) not interacting.
D) interacting but only mildly with little effect on disequilibrium state.

Accepted Answer

Linkage disequilibrium (D) being equal to a negative value (as indicated by the subtraction in the formula) suggests that the alleles are in repulsion, meaning they are less likely to be inherited together than expected by chance.

Question 19

Selection can generate novel phenotypes by
A) drift causing the creation of a new phenotype.
B) increasing the probability of novel allele combinations.
C) genetic hitchhiking and selective sweeps.
D) creating linkage disequilibrium.

Accepted Answer

Selection can increase the probability of novel allele combinations by favoring individuals with certain traits or genotypes. This can lead to the emergence of new phenotypes that may be better adapted to their environment. Drift, genetic hitchhiking and selective sweeps, and linkage disequilibrium can also play a role in evolution, but they do not directly generate novel phenotypes.

Question 20

The observation of an offspring phenotype outside of the range of parental phenotypes is most likely due to
A) additive genetic effects.
B) mutation.
C) genetic drift.
D) latent variation.

Accepted Answer

Latent variation refers to the presence of genetic variation that is not expressed in the parental phenotypes but can be revealed in the offspring, leading to phenotypes outside the parental range.

Quiz 9: Evolution at Multiple Loci

Consider a population with two loci (A, B) , each with two alleles (A, a; B, b) . What are the allele frequencies in this population if the haplotype frequencies are AB = 0.35, Ab = 0.15, aB = 0.35, ab = 0.15?

The statistical association of alleles at different loci is referred to as

Which of the following is most likely to break up linkage disequilibrium?

Hardy-Weinberg at two loci The figure demonstrates Hardy-Weinberg frequencies at two loci. Which term represents the expected offspring haplotype frequencies for a cross between parents with aB and aB gametes?

The rediscovery of Mendelian inheritance caused increased scrutiny of Charles Darwin's theory of natural selection because of an apparent conflict in the two concepts. This conflict was based on the observation that Darwin focused on continuous traits, whereas Mendelian genetics deals with

What is one reason why antibiotic resistance does not always disappear as quickly as one might expect after large-scale antibiotic use is ended?

Narrow-sense heritability is defined as the genetic variation divided by the variation.

What is the largest possible value that linkage disequilibrium can reach if all allele frequencies are 0.5?

What two major concepts in biology were unified in the middle of the twentieth century?

Consider two loci located close together on a single chromosome. These loci

A haplotype is

Genotypic adaptive landscapes may better represent true adaptive landscapes than phenotypic adaptive landscapes when

In quantitative genetic terms, a phenotypic value can be expressed as

Which of the following occurs when there is so much Mendelian variation within a population that not all possible genotypes could be represented in any given generation?

Assuming the value of linkage disequilibrium (D) is positive, recombination will generate

Which of the following processes that can create linkage disequilibrium is illustrated in the figure?

If the value of linkage disequilibrium (D) is equal to -0.25, one can infer that the alleles are

Selection can generate novel phenotypes by

The observation of an offspring phenotype outside of the range of parental phenotypes is most likely due to