Question 1

What is a random change in allele frequencies over time known as?

Accepted Answer

A random change in allele frequencies over time is known as genetic drift. This can occur when a small population is isolated, resulting in a loss of genetic variation due to chance events such as random deaths or mutations. Over time, genetic drift can lead to changes in the genetic makeup of a population and the emergence of new genetic traits.

Question 2

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

Accepted Answer

The phenomenon described suggests disruptive selection, which favors extreme phenotypes over intermediate ones. In this case, birds with either wide or sharp narrow beaks are better adapted to their environment than those with medium-sized beaks.

Question 3

What effect does natural selection have on population variation?

Accepted Answer

Natural selection tends to decrease variation in a population by selecting for certain traits that are advantageous for survival and reproduction, resulting in the spread of those traits throughout the population. This can lead to a reduction in diversity within the population over time. However, it is important to note that natural selection can also increase variation in certain circumstances, such as in response to environmental changes or when different traits are advantageous in different environments.

Question 4

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%.What is this is an example of?

Accepted Answer

The shift in frequencies of traits (green and brown coloration) within a population over a relatively short period of time (two generations) is an example of microevolution. Macroevolution refers to larger-scale evolutionary changes, such as the emergence of entirely new species, while millievolution and nanoevolution are not commonly used terms in evolutionary biology.

Question 5

What is the cause of spontaneous mutation?

Accepted Answer

The cause of spontaneous mutation is not fully understood, and it may occur randomly without any known external factor. However, certain genetic and environmental factors may increase the likelihood of spontaneous mutations.

Question 6

Which of the following defines natural selection?

Accepted Answer

Natural selection is the nonrandom elimination of alleles that do not confer an advantage in a particular environment. This process leads to a greater frequency of advantageous traits within a population over time, and is often summarized as "survival of the fittest". However, it is important to note that "fitness" in this context refers to reproductive success rather than physical strength or prowess. Natural selection is also not an upward progression or a result of random changes in organisms' genetic make-up.

Question 7

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,what was the percentage of genotypes found to be?

Accepted Answer

According to the Hardy-Weinberg equation, the expected genotype frequencies are p^2, 2pq, and q^2, where p is the frequency of one allele and q is the frequency of the other allele. In this case, the frequency of the P allele is 0.35, so the frequency of the p^2 genotype is (0.35)^2 = 0.1225. Similarly, the frequency of the q^2 genotype is (0.65)^2 = 0.4225. Finally, the frequency of the 2pq genotype is 2(0.35)(0.65) = 0.455, which is closest to option B, where p^2 = 0.35, 2pq = 0.00, and q^2 = 0.65.

Question 8

What are patrilocal societies expected to display?

Accepted Answer

In patrilocal societies, women move to live with their husband's family, leading to greater mtDNA diversity as women from different genetic backgrounds join the community, while men remain in their birthplace, resulting in less Y chromosome diversity.

Question 9

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

Accepted Answer

Directional selection favors individuals with extreme phenotypes, leading to a shift in the population towards one extreme. In this case, the drought conditions would have selected for individuals with wider beaks well adapted to breaking open tough seeds, leading to a higher frequency of this trait in the population.

Question 10

An individual who displays the disease sickle-cell anemia must have inherited the deleterious allele from both phenotypically normal parents.What,therefore,is this individual?

Accepted Answer

An individual with sickle-cell anemia must have inherited two recessive alleles (sickle-cell allele) from both parents as it is a recessive genetic disorder. Therefore, the individual is homozygous with two recessive alleles.

Question 11

Why are frameshift mutations more likely to have an impact at the phenotypic level?

Accepted Answer

Frameshift mutations cause a shift in the reading frame of the genetic message, leading to the formation of a protein with an altered amino acid sequence. This alteration in the amino acid sequence can result in a protein with no function, which can have a significant impact at the phenotypic level.

Question 12

What is the mutation known as trisomy 21,in which an extra copy of chromosome 21 is present,more commonly known as?

Accepted Answer

Trisomy 21 is more commonly known as Down syndrome.

Question 13

Fitness trade-off refers to selection favoring which genotype?

Accepted Answer

Fitness trade-off refers to the phenomenon where selection favors a genotype that maintains a balance between two opposing traits. In this case, heterozygous individuals are favored because they have a balanced expression of both dominant and recessive alleles, allowing for greater flexibility and adaptability in changing environments. Homozygous dominant individuals may have an advantage in stable environments, but may be at a disadvantage if there is a sudden change in the environment. Homozygous recessive individuals may have an advantage in unstable environments, but may be at a disadvantage if the environment becomes stable again. Therefore, heterozygous individuals are the best choice as they have a balance of both traits and are better equipped to handle changing environments.

Question 14

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.What does this demonstrate?

Accepted Answer

The increased frequency of familial hypercholesterolemia in the Afrikaner population of South Africa is a result of the founder effect. This is because their ancestors carried the genetic mutation that causes the disease, and this small group of founders then passed on this mutation to a larger proportion of their descendants due to genetic isolation and restricted gene flow. This is a clear example of how the founder effect can lead to the increased prevalence of a genetic disorder in a population.

Question 15

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,what can we assume?

Accepted Answer

Hardy-Weinberg equilibrium assumes that mating in a population is random, so if the genotype frequencies remain the same across generations, it suggests that mating in this population is random, rather than being influenced by factors such as negative assortative mating or mutations. The fact that the frequencies remained the same also suggests that the population is large enough to avoid significant genetic drift. Therefore, we can assume that the population is in Hardy-Weinberg equilibrium.

Question 16

What is a cause of the absence of the A and B alleles in Native American populations?

Accepted Answer

The absence of the A and B alleles in Native American populations is due to the founder effect. When a small group breaks away from a larger population to start a new population, the genetic variation of the smaller group is limited to that of the founders. In this case, the founders of Native American populations did not have the A and B alleles, so subsequent generations of Native Americans also did not have these alleles as the population grew and expanded.

Question 17

Will a frameshift mutation have a larger effect than a point mutation? Why or why not?

Accepted Answer

A frameshift mutation will have a larger effect because it shifts the reading frame of the codons downstream and causes all subsequent amino acids to be incorrect, leading to a non-functional protein or premature termination. A point mutation, on the other hand, may only affect a single amino acid, possibly altering protein function but not necessarily causing significant harm.

Question 18

You are reading a scientific article about cheetahs that have stripes down their backs instead of spots.The article refers to this as a genetic mutation.Though they have no negative impact on the cheetahs' fitness,why are the stripes nevertheless considered a genetic mutation?

Accepted Answer

Mutations can be adaptively neutral, meaning they have no negative or positive impact on an organism's fitness. The fact that the stripes on the cheetahs have no negative impact on their fitness suggests that the mutation is neutral.

Question 19

What type of animal does the best-documented case of industrial melanism involve?

Accepted Answer

The best-documented case of industrial melanism involves peppered moths. During the Industrial Revolution, the prevalence of dark-colored moths increased in polluted areas as they were better camouflaged on soot-covered tree trunks, whereas light-colored moths were easier targets for predators.

Question 20

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

Accepted Answer

The evolution of the modern horse from a dog-sized ancestral species with multiple digits to a horse with a single hoof on each limb is an example of macroevolution. This is because it involves dramatic changes in the structure and function of the organism, including the loss of digits and the adaptation to running on a single toe.

Quiz 4: Genes and Their Evolution: Population Genetics