Question 1

Consider three populations of a plant species, each isolated from other populations of the same species. Population X has contained approximately 100 individuals in each generation for the past 200 generations. Population Y has contained approximately 10 000 individuals in each generation for the past 200 generations. Population Z has contained approximately 1 million individuals in each generation for the past 200 generations. If genetic drift is the only evolutionary process acting on these populations, how can we expect the amount of genetic variation to differ among these populations?

Accepted Answer

The amount of genetic variation is expected to be highest in population Z, as it has a large population size and therefore is less affected by genetic drift. Population Y has an intermediate population size and is expected to have intermediate amounts of genetic variation. Population X has a small population size and is expected to have the lowest amount of genetic variation, as it is most affected by genetic drift.

Question 2

Which of the following types of allele would we expect to have the lowest frequency in a population?

Accepted Answer

Harmful dominant alleles are the least likely to be present in a population as they are more likely to be negatively selected against and eliminated from the gene pool. Harmful recessive alleles can be carried in heterozygous individuals and not affect their fitness, allowing them to persist in the population at low frequencies. Beneficial alleles, whether dominant or recessive, are more likely to increase in frequency over time due to positive selection.

Question 3

What term refers to the alleles of all of the genes of every individual in a population?

Accepted Answer

The term that refers to the alleles of all of the genes of every individual in a population is the gene pool. The gene pool consists of all the genetic information present in a population, including both dominant and recessive alleles. The gene pool is one of the key factors that determines the genetic variability of a population and is important in understanding how populations evolve over time. Choice A (polygenic) refers to traits that are controlled by multiple genes, while choice B (heterozygous) refers to having two different alleles for a particular gene. Choice D (random assortment) refers to how chromosomes segregate during meiosis.

Question 4

Different forms of a particular gene are known as

Accepted Answer

Different forms of a particular gene are called alleles. Chromosomes refer to the structures that contain genes, polygenic refers to traits that are influenced by multiple genes, and pleiotropic refers to genes that affect multiple traits.

Question 5

Consider a situation in which overharvesting causes the number of fish in a population to become drastically smaller, which causes genetic variation in that fish to decrease over a few generations. This is an example of

Accepted Answer

The scenario described is consistent with the bottleneck effect, which occurs when a large portion of a population dies off, leaving only a small number of individuals to repopulate. This can result in reduced genetic diversity due to the limited number of individuals carrying the surviving genes.

Question 6

Many genetic diseases have severe or lethal effects in the homozygous form, yet alleles for these diseases are not entirely removed by natural selection. Explain how dominance relationships among alleles allow deleterious mutations to remain in a population.

Accepted Answer

The answer of Many genetic diseases have severe or lethal...

Question 7

The shuffling of genes that occurs when DNA is copied during meiosis is known as

Accepted Answer

Recombination or crossing-over is the process by which genetic material is exchanged between homologous chromosomes during meiosis I. This results in new combinations of genes on each chromosome and is the primary mechanism for generating genetic diversity.

Question 8

Describe the difference between synonymous and nonsynonymous mutation. Which type is more likely to be affected by natural selection, and why?

Accepted Answer

The answer of Describe the difference between synonymous and nonsynonymous...

Question 9

For mutations that enter a population of a diploid organism, which type of mutation is most likely to be affected by natural selection when it first appears?

Accepted Answer

Nonsynonymous dominant mutations are most likely to be affected by natural selection when they first appear because they produce a change in the phenotype even when present in only one copy (heterozygous). This can lead to either positive or negative selection depending on the effect on fitness. Synonymous mutations have no effect on the phenotype and therefore are unlikely to be affected by natural selection. Nonsynonymous recessive mutations may not have an effect on the phenotype unless present in both copies (homozygous) and are therefore less likely to be affected by natural selection initially.

Question 10

The rate at which allele frequencies change because of genetic drift is

Accepted Answer

Genetic drift is the random fluctuation of allele frequencies in a population. In small populations, chance events can have a greater impact on the gene pool, leading to more rapid changes in allele frequencies. Therefore, the rate of allele frequency change due to genetic drift is highest in small populations.

Question 11

Chickens with the dominant allele at the frizzle gene produce curly feathers, have very high body temperature, and lay few eggs. This is an example of

Accepted Answer

This is an example of pleiotropy, where one gene has multiple effects on an individual's phenotype. The frizzle gene affects feather shape, body temperature, and egg-laying ability.

Question 12

Two of the genes that affect coat colour in horses are the extension gene and the cream dilution gene. The dominant E allele at the extension gene generates black coats, while the recessive e allele produces red coats. The coat colour caused by the extension gene is not altered if the horse is a homozygote for the C allele at the cream dilution gene. However, if the horse is a homozygote for the C^Cr allele at the cream dilution gene, it will have a white coat regardless of the extension genotype. This interaction between the extension and the cream dilution gene is an example of

Accepted Answer

The interaction between the extension and the cream dilution gene is an example of epistasis, where the action of one gene masks or modifies the effect of another gene. In this case, the cream dilution gene modifies the expression of the extension gene, resulting in horses with the C^Cr allele having a white coat regardless of their extension genotype.

Question 13

What process creates new alleles in a population?

Accepted Answer

Mutation is the process that creates new alleles in a population. Mutations can occur spontaneously or be induced by external factors such as radiation or chemicals. A mutation can alter the sequence of DNA, leading to the creation of a new allele that was not previously present in the population.

Question 14

What term describes making new combinations of alleles using existing genetic variation across many chromosomes?

Accepted Answer

Random assortment is the process by which maternal and paternal chromosomes align independently during meiosis, resulting in new combinations of alleles on different chromosomes, which creates genetic variation in offspring. Pleiotropy, epistasis, and mutation refer to different genetic concepts that do not necessarily involve combining existing genetic variation across many chromosomes.

Question 15

Which is (are) correct about founder effect?
I. Founder effect occurs when individuals are transplanted to a new location.
II. Founder effect produces new alleles.
III. Founder effect reduces genetic variation.

Accepted Answer

Founder effect occurs when a small group of individuals separates from a larger population and establishes a new population elsewhere. Hence, option I is correct. Founder effect reduces genetic variation because only a small number of individuals carry a subset of genes from the original population, which may not reflect the overall genetic diversity of the original population. Therefore, option III is also correct. However, founder effect does not produce new alleles as the original population is not changed, only a subset of it is taken to a new location. Hence, option II is incorrect.

Question 16

Consider a gene that affects fur colour in mice. This gene has two alleles, A and A. If AA mice have white fur, Aa mice have grey fur, and aa mice have black fur, how would we describe the effect of these alleles?

Accepted Answer

The alleles A and a are codominant because the heterozygous Aa mice have a phenotype (grey fur) that is distinct from both homozygous phenotypes (white fur for AA and black fur for aa).

Question 17

Consider a gene that affects number of seeds in a plant. This gene has two alleles, G and G. If GG plants produce 50 seeds, Gg plants produce 50 seeds, and gg plants produce 25 seeds, how would we describe the effect of these alleles?

Accepted Answer

GG plants and Gg plants have the same phenotype (producing 50 seeds), indicating that G is dominant over g. gg plants have a different phenotype (producing 25 seeds), indicating that g is recessive when paired with G.

Question 18

A trait that is determined by multiple genes is referred to as

Accepted Answer

A trait that is determined by multiple genes is referred to as polygenic. Pleiotropy refers to a single gene affecting multiple traits, and homozygous and heterozygous refer to the genetic makeup of an individual at a particular gene locus.

Question 19

A process that occurs when genetic variation is lost because of random variation in mating, mortality, fecundity, and inheritance is known as

Accepted Answer

Genetic drift is the process where genetic variation is lost due to random events, such as chance mating or mortality. It is a random process and not driven by natural selection or mutation. Stabilizing selection and disruptive selection are both mechanisms of natural selection, whereas mutation is a process that introduces new genetic variation rather than removing it.

Question 20

Clonal animals do not reshuffle their genes through genetic recombination, whereas sexually reproducing animals do. Explain how this difference could affect how pathogens interact with clonal animals and how they interact with sexually reproducing animals.

Accepted Answer

The answer of Clonal animals do not reshuffle their genes...

Quiz 7: Evolution and Adaptation