Question 1

Studies of Galapagos finches have found that at certain points in time all finches on the island have either wide beaks or sharp narrow beaks.The type of evolution that leads to this phenotype distribution is _______ selection.

Accepted Answer

Disruptive selection is when extreme values of a trait are favored over intermediate values, leading to a bimodal distribution of phenotypes. In the case of the Galapagos finches, at certain times there may be two distinct food sources that require different beak sizes, selecting for either wide or narrow beaks and leading to a bimodal distribution of beak sizes.

Question 2

A study of Galapagos finches after a long period of drought found that all species of finch on one of the islands had wide beaks well adapted to breaking open seeds.The type of evolution that leads to this phenotype distribution is _______ selection.

Accepted Answer

Directional selection occurs when a particular phenotype is favored over other phenotypes, causing a shift in the distribution of phenotypes in a population. In this case, the wide beaks of the finches were favored during the drought because they were better able to break open seeds, leading to an increase in the frequency of this trait in the population.

Question 3

Patrilocal societies are expected to display:

Accepted Answer

The answer of Patrilocal societies are expected to display:
...

Question 4

Fitness trade-off refers to selection favoring which genotype?

Accepted Answer

Fitness trade-off occurs when individuals with both dominant and recessive alleles have different advantages and disadvantages, leading to selection favoring the heterozygous genotype. This is because the heterozygous genotype can take advantage of the benefits of both alleles while minimizing the negative effects of each. Therefore, option C (heterozygous) is the favored genotype in this case.

Question 5

The best-documented case of industrial melanism involves:

Accepted Answer

The best-documented case of industrial melanism involves peppered moths. This is a phenomenon where there was a shift in moth populations from mostly light-colored to mostly dark-colored due to environmental pollution during the Industrial Revolution.

Question 6

Frameshift mutations are more likely to have an impact at the phenotypic level because they:

Accepted Answer

Frameshift mutations involve the insertion or deletion of nucleotides, which changes the reading frame of the codons in the mRNA sequence. This often results in a completely different sequence of amino acids in the resulting protein, which may lead to a non-functional or partially functional protein. This can have a significant impact at the phenotypic level because proteins are the functional molecules in cells and play important roles in various cellular processes.

Question 7

You are reading a scientific article about cheetahs that have stripes instead of spots.The article refers to this as a genetic mutation.Though you see they have no negative impact on the cheetahs' fitness, the stripes are nevertheless considered a genetic mutation because mutations:

Accepted Answer

Mutations are changes in the genetic material that can lead to variations in traits, such as the appearance of stripes instead of spots on cheetahs. These changes can have a range of effects: they can be advantageous, disadvantageous, or neutral with respect to an organism's fitness. Thus, all the options provided are correct aspects of genetic mutations.

Question 8

The absence of the A and B alleles in Native American populations is a result of:

Accepted Answer

The founder effect is the reduction in genetic variation that occurs when a small subset of a larger population establishes a new colony. This subset may not have the full range of alleles present in the larger population, which can lead to certain alleles being overrepresented or completely absent in the new population. The absence of the A and B alleles in Native American populations is thought to be a result of the founder effect, as the ancestors of modern Native Americans migrated across the Bering Strait and formed new populations in the Americas. Over time, the A and B alleles may have been lost due to chance events in the founding populations, rather than through natural selection, gene flow, or mutation.

Question 9

What effect does natural selection have on population variation?

Accepted Answer

Natural selection acts on variations within a population and favors certain traits over others that increase an individual's chances of survival and reproduction. As a result, over time, the frequency of certain traits in the population will increase, while others will decrease, ultimately decreasing the overall variation within the population.

Question 10

A genetic study conducted over multiple generations found that the frequency of genotypes in the first generation were AA: 0.36, Aa: 0.48, aa: 0.16.In the second generation, genotype frequencies shifted to AA: 0.16, Aa: 0.48, aa: 0.36.According to the Hardy-Weinberg equilibrium, we can assume:

Accepted Answer

The fact that there was a shift in gene frequencies between the first and second generations suggests that something has disturbed the Hardy-Weinberg equilibrium. Gene flow, which is the movement of individuals and their genes between populations, could have contributed to this shift. However, the shift could also be due to nonrandom mating, which means that individuals are not mating randomly with respect to their genotype (e.g. individuals with similar genotypes are more likely to mate). Therefore, both option B (gene flow) and option C (nonrandom mating) could be the cause of the shift in gene frequencies.

Question 11

The evolution of the modern horse with a single hoof on each limb from a dog-sized ancestral species with multiple digits is an example of:

Accepted Answer

The evolution of the modern horse from its dog-sized ancestor with multiple digits involved significant changes in morphology, behavior, and ecology over time, which is an example of macroevolution.

Question 12

Why is the incidence of sickle-cell anemia an excellent example of a "balanced polymorphism," in which two or more alleles are maintained by natural selection in a population?

Accepted Answer

The answer of Why is the incidence of sickle-cell anemia...

Question 13

In a classroom taste test for PTC the genotype frequency was determined to be P = 0.35 and Q = 0.65.After applying the Hardy-Weinberg equation, the percentage of genotypes was found to be as follows:

Accepted Answer

According to the Hardy-Weinberg equation, p2 + 2pq + q2 = 1. Using the given frequencies, we can solve for each genotype frequency as follows:
p2 = P x P = 0.35 x 0.35 = 0.1225
2pq = 2 x P x Q = 2 x 0.35 x 0.65 = 0.455
q2 = Q x Q = 0.65 x 0.65 = 0.4225
Rounding to two decimal places, we get the genotype frequencies of p2 = 0.12, 2pq = 0.46, and q2 = 0.42. Therefore, the best choice is B.

Question 14

What is a polymorphic trait? Provide two examples of polymorphic traits in modern humans, and give one example of a monomorphic trait.

Accepted Answer

The answer of What is a polymorphic trait? Provide two...

Question 15

A random change in allele frequencies over time is known as:

Accepted Answer

Genetic drift refers to the random fluctuations in allele frequencies in a small population due to chance events, such as births, deaths, and genetic mutations. Gene flow (B) refers to the transfer of genetic material from one population to another, while admixture (C) refers to the mixing of genetic material from different populations. Gene migration (D) is an ambiguous term and not commonly used in population genetics.

Question 16

An individual who displays the disease sickle-cell anemia must have inherited the deleterious allele from both phenotypically normal parents.This individual is therefore:

Accepted Answer

Sickle-cell anemia is an autosomal recessive disorder, which means that an individual must inherit two copies of the deleterious allele (one from each parent) in order to display the disease phenotype. Therefore, the individual in question is homozygous for the recessive allele that causes sickle-cell anemia, and has no functional copies of the normal allele.

Question 17

Familial hypercholesterolemia, an autosomal dominant disease, is five times more frequent in the Afrikaner population of South Africa than in the original population of Europe from which the ancestors to the Afrikaners immigrated.This represents an example of:

Accepted Answer

The increased frequency of familial hypercholesterolemia in the Afrikaner population is an example of the founder effect, which occurs when a small group of individuals establishes a new population with a limited genetic diversity. The original European population had a lower frequency of the disease, but the Afrikaner population descended from a small group of individuals who brought a high frequency of the disease-causing allele to South Africa, resulting in a higher frequency of the disease in the Afrikaner population. Natural selection and kin selection are not relevant to this example, and there is no evidence of a bottleneck event.

Question 18

Spontaneous mutation is the result of:

Accepted Answer

Spontaneous mutations occur randomly and without any external causes such as x-rays, toxic chemicals or UV radiation. They are caused by natural errors in DNA replication, recombination or repair.

Question 19

A genetic study conducted over two generations found that the frequencies of genotypes in the first generation were AA: 0.36, Aa: 0.48, aa: 0.16.In the second generation, genotype frequencies remained the same.According to the Hardy-Weinberg equilibrium, we can assume:

Accepted Answer

According to Hardy-Weinberg equilibrium, the genotype frequencies remain constant over generations if mating is random and there are no evolutionary forces acting on the population such as mutations, selection, genetic drift, or migration. Therefore, the fact that the genotype frequencies remained the same between the two generations suggests that mating in this population is random. Therefore, option C is the correct answer. Options A and B are incorrect since they suggest the action of specific evolutionary forces, whereas the information provided in the question does not support that conclusion. Option D is incorrect since the size of the population is not given, and the question does not provide evidence to suggest that the population is small.

Question 20

The mutation known as trisomy 21, in which an extra copy of chromosome 21 is present, is more commonly known as _______ syndrome.

Accepted Answer

Trisomy 21 is commonly known as Down syndrome.

Quiz 4: Genes and Their Evolution: Population Genetics