Question 1

A study of Darwin's finches after a long period of drought found that all species of finch on one of the islands had developed wide beaks in order to break open seeds. The type of evolution that leads to this phenotype distribution is:

Accepted Answer

Directional selection occurs when environmental pressures favor one extreme phenotype over others, leading to a shift in the population's trait distribution, such as the development of wide beaks in finches to access seeds during drought.

Question 2

Fitness trade-off refers to selection favoring which genotype?

Accepted Answer

The fitness trade-off occurs when there is a compromise between two traits, and there is no one genotype that is favored over the others. In the case of heterozygous individuals, they have a greater genetic diversity, which can provide a selective advantage when faced with changing environmental conditions. Therefore, heterozygous individuals may be favored in certain situations, making choice C the best option.

Question 3

Studies of Darwin's 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:

Accepted Answer

This phenotype distribution is the result of disruptive selection, where extreme phenotypes (wide or narrow beaks) are favored over intermediate phenotypes. This can occur in environments where two or more distinct niches exist, each favoring a different phenotype.

Question 4

The best-documented case of industrial melanism involves:

Accepted Answer

The best-documented case of industrial melanism involves peppered moths, which became darker in color due to natural selection during the industrial revolution in England.

Question 5

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

Accepted Answer

Frameshift mutations result in a change to the reading frame of a gene, causing a shift in the codons that are translated into amino acids to produce a protein. This can result in the creation of a completely altered amino acid sequence, often leading to a protein with no function. As a result, frameshift mutations are more likely to have a significant impact at the phenotypic level.

Question 6

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

Accepted Answer

A random change in allele frequencies over time is specifically referred to as genetic drift, making A the correct answer. Gene flow, admixture, and gene migration all involve the movement of genetic material but not necessarily a random change in allele frequencies.

Question 7

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

Accepted Answer

The evolution of the modern horse with a single hoof on each limb from a dog-sized ancestor with multiple digits is an example of macroevolution, which refers to large-scale evolutionary changes over long periods of time, such as the emergence of new species or groups of organisms.

Question 8

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:

Accepted Answer

Mutations are changes in the DNA sequence and can lead to variations in traits. They can be beneficial, harmful, or neutral, affecting the organism's phenotype or fitness in various ways.

Question 9

The vector for transmitting the malarial parasite to humans is:

Accepted Answer

The malarial parasite is transmitted to humans through the bites of infected mosquitoes. Mosquitoes become infected with the parasite when they feed on the blood of an infected person. When the infected mosquito bites another person, the parasite is transferred into that person's bloodstream, causing malaria.

Question 10

What effect does natural selection have on population variation?

Accepted Answer

Natural selection decreases variation within a population by selecting individuals with certain advantageous traits to survive and reproduce, while eliminating those with less favorable traits. This results in a higher frequency of the advantageous trait in the population, reducing variation.

Question 11

In a classroom taste test for PTC the genotype frequency was determined to be P = .35 and Q = .65. After applying the Hardy-Weinberg equation, the percentage of genotypes was found to be as follows:

Accepted Answer

When applying the Hardy-Weinberg equation, the percentage of genotypes should be P2 + 2pq + q2 = 1, where P and Q represent the frequencies of the two alleles and p and q represent the frequencies of the two genotypes. Using the given genotype frequencies, we can calculate P and Q as follows:

P = F1F1 = (0.35 * 2 + 0.65) / 2 = 0.675
Q = F1S1 = (0.35 + 0.65 * 2) / 2 = 0.325

Then, we can use the equation to calculate the genotype frequencies:

F1F1F1S1F1S1S1S1 = p2 = (0.675)2 = 0.456
F1F1F1S1F1S1S1U1 = 2pq = 2 * 0.675 * 0.325 = 0.438
F1S1F1S1F1S1S1S1 = q2 = (0.325)2 = 0.105

Therefore, the correct answer is B.

Question 12

Patrilocal societies are expected to display:

Accepted Answer

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

Question 13

Spontaneous mutation is the result of:

Accepted Answer

Spontaneous mutation is a mutation that occurs naturally in the genetic material of an organism, without any external influence such as radiation or chemicals. The causes of spontaneous mutations are largely unknown, but they are thought to occur randomly during DNA replication or repair.

Question 14

Over a period of two generations, the frequency of green dung beetles in a population shifts from 75% to 71% while the frequency of brown dung beetles within this population shifts from 25% to 29%. This is an example of:

Accepted Answer

This is an example of microevolution, which refers to small changes within a population over a relatively short period of time. The shift in frequency of green and brown dung beetles is a change in the genetic makeup of the population, but it does not result in the formation of a new species or a significant change in the overall characteristics of the population.

Question 15

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

An individual displaying the disease sickle-cell anemia must have inherited the deleterious allele from both parents, meaning they must be homozygous recessive for the gene that codes for hemoglobin. They do not have a dominant allele to mask the expression of the recessive allele. Choice (A) is incorrect because homozygous dominant individuals would not display the disease. Choice (C) is incorrect because heterozygous individuals are carriers of the sickle-cell allele but do not display the disease. Choice (D) is not a valid term in genetics.

Question 16

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 17

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 Hardy-Weinberg equilibrium, we can assume:

Accepted Answer

Hardy-Weinberg equilibrium assumes random mating and no other factors that could change gene frequencies (such as mutations or selection). Since the genotype frequencies remained constant between generations, we can assume that the population was in Hardy-Weinberg equilibrium, and thus mating was random. Choices A, B, and D can be ruled out because they all suggest that some factor other than random mating has impacted gene frequencies.

Question 18

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

Accepted Answer

Trisomy 21 is commonly known as Down syndrome. Turner syndrome is due to monosomy X, Klinefelter's syndrome is due to an extra X chromosome in males, and Williams syndrome is caused by a deletion of genetic material on chromosome 7.

Question 19

Familial hypercholesterolemia, an autosomal dominant disease, is five times more frequent in the Afrikaner population of South Africa than in the population of Europe or the United States. This represents an example of:

Accepted Answer

The high frequency of familial hypercholesterolemia in the Afrikaner population is most likely due to a founder effect, where a small group of individuals with the disease migrated to South Africa and their descendants make up a large proportion of the Afrikaner population. This is supported by the fact that the disease is much less frequent in Europe and the United States, suggesting that it did not arise independently in those populations. Natural selection and kin selection are not the most likely explanations for this pattern, and a bottleneck is not supported by the high frequency of the disease in the Afrikaner population.

Question 20

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

Accepted Answer

The absence of the A and B alleles in Native American populations is likely a result of the founder effect. This occurs when a small group of individuals establishes a new population, and by chance, the gene pool of the new population differs from that of the original population. In this case, the group of individuals that migrated to the Americas from Asia likely had a low frequency or absence of the A and B alleles, which became fixed in the new population through genetic drift.

Quiz 4: Genes and Their Evolution: Population Genetics