Question 1

What general effect does random genetic drift have on populations?
1)It reduces the dominant homozygosity.
2)It reduces the heterozgosity.
3)It reduces the recessive homozygosity.

Accepted Answer

Random genetic drift reduces the genetic variation within a population, which leads to a reduction in heterozygosity (the proportion of individuals in a population that are heterozygous). It does not necessarily have a significant effect on the dominant or recessive homozygosity.

Question 2

What causes allele frequencies to change unpredictably in populations because of reproductive uncertainties?

Accepted Answer

Random genetic drift causes unpredictable changes in allele frequencies due to chance events, such as random mutations or chance fluctuations in reproductive success. This is particularly pronounced in small populations, where chance events can have a greater impact on allele frequencies. Random genetic abnormalities, natural selection, and artificial selection are all forces that can cause predictable changes in allele frequencies, while random mating refers to individuals choosing mates randomly rather than based on specific traits or characteristics.

Question 3

Which of the following is a type of non-random mating?

Accepted Answer

Consanguinous mating (mating between individuals who are closely related) and assortative mating (mating based on phenotypic similarities or differences) are both types of non-random mating. They involve specific selection criteria, unlike random mating where mates are chosen regardless of genetic relationship or phenotypic similarities.

Question 4

Which assumption of the Hardy-Weinberg principle is violated by the concept of population subdivision?

Accepted Answer

Population subdivision violates the assumption that allele frequencies are uniform throughout the population, as it implies that there are subpopulations with potentially different allele frequencies.

Question 5

Selection that favors intermediate values of a trait at the expense of extreme values is known as

Accepted Answer

Stabilizing selection favors intermediate values of a trait, as extreme values are selected against. The other options, directional and disruptive selection, favor one or both extremes of a trait.

Question 6

The A-B-O blood types are determined by three alleles I^A,I^B,and i.In one population the frequency of individuals who are homozygous for type A blood is 0.063,the frequency of individuals who are homozygous for type B blood is 0.015,and the frequency of individuals who are blood type O is 0.44.What is the frequency of the i allele?

Accepted Answer

The frequency of the i allele can be calculated using the Hardy-Weinberg principle. Given that the frequency of type O blood (ii) is 0.44, and knowing that this represents the homozygous condition (ii), we can calculate the frequency of the i allele as the square root of 0.44, which gives us 0.663. This is because the frequency of type O blood is equal to the frequency of the i allele squared (p^2 for homozygous conditions in Hardy-Weinberg).

Question 7

When a population is a single interbreeding unit,it is said to be

Accepted Answer

When a population is a single interbreeding unit, it is said to be panmictic. Panmictic means that individuals in the population have an equal chance of mating with any other member of the population. This ensures that genes are randomly distributed among the population and that there is no genetic differentiation between subgroups within the population. Non-panmictic populations, on the other hand, have some barriers to interbreeding, which can lead to genetic differentiation between subgroups within the population. Heterozygous and homozygous refer to the genetic makeup of individuals, and are not related to the concept of panmixia.

Question 8

Which of the following prevent the Hardy-Weinberg principle from applying to a population?

Accepted Answer

The principle assumes that all individuals have an equal chance of survival and reproduction. If this is not the case, then the allele frequencies will be affected over time. A, C, and D are conditions that promote the principle, so they do not prevent it from applying.

Question 9

At the level of the phenotype,natural selection influences the

Accepted Answer

Natural selection influences the distribution of quantitative traits, which are traits that vary continuously and are influenced by both genetic and environmental factors. Natural selection acts on the variation in these traits and favors certain variants over others, leading to changes in the frequency of alleles that contribute to the variation. However, it does not directly influence the distribution of genotypes or alleles themselves.

Question 10

Which of the following occurs when genotypes differ in the ability to survive and reproduce?

Accepted Answer

This is the classic definition of natural selection. Genotypes that are better adapted to their environment are more likely to survive and reproduce, passing on their advantageous traits to their offspring.

Question 11

Which of the following is most effective at fixing the recessive allele in a population?

Accepted Answer

Selection for a recessive allele is most effective at fixing the recessive allele in a population because it directly increases the frequency of that allele by favoring its expression and survival.

Question 12

At the level of the gene,natural selection changes the frequencies of

Accepted Answer

Natural selection refers to the process where certain traits or alleles become more common in a population due to their fitness advantage, which leads to higher survival and reproduction rates. At the level of the gene, natural selection acts on specific alleles, and thus changes their frequencies in populations. Therefore, the correct choice is D - natural selection changes the frequencies of alleles in populations. The other choices (A, B, C, and E) are not accurate because they refer to either genotypes (A and B) or biomes (A and C), which are not directly affected by natural selection at the gene level.

Question 13

What effect does consanguineous mating and assortative mating have on genotypic frequencies in populations?
1)Reduce the frequency of homozyotes
2)Increase the frequency of homozygotes
3)Reduce the frequency of heterozygotes

Accepted Answer

Consanguineous mating (mating between relatives) and assortative mating (mating based on similar traits) both tend to increase the frequency of homozygotes in a population because they increase the likelihood that individuals with similar genetic backgrounds or traits will mate. This also leads to a reduction in the frequency of heterozygotes, as there is a higher chance of mating between individuals with similar alleles.

Question 14

The A-B-O blood types are determined by three alleles I^A,I^B,and i.In one population the frequency of individuals who are homozygous for type A blood is 0.063,the frequency of individuals who are homozygous for type B blood is 0.015,and the frequency of individuals are blood type O is 0.44.What is the frequency of individuals who are heterozygous for type A blood?

Accepted Answer

The answer of The A-B-O blood types are determined by...

Question 15

The intensity of natural selection is quantified by the

Accepted Answer

The selection coefficient is a measure of the relative decrease in the reproductive success of a particular genotype or phenotype, compared to other genotypes or phenotypes in the same population. It is a widely used measure of the intensity of natural selection. The other options, such as correlation coefficient or cosanguinous coefficient, are not necessarily measures of the intensity of natural selection. Fitness number is not a commonly used term in evolutionary biology.

Question 16

Selection that favors extreme values of a trait at the expense of intermediate values is known as

Accepted Answer

Disruptive selection favors extreme values of a trait, while selecting against intermediate values. Directional selection favors one extreme value of a trait over the other, while stabilizing selection favors intermediate values and selects against extreme values. Therefore, choice B best describes the scenario where extreme values are favored at the expense of intermediate values.

Question 17

In a population that experiences migration (i.e.the merging of two separate populations),why are observed allelic and genotypic frequencies different than what is predicted by the Hardy-Weinberg equilibrium?

Accepted Answer

In a population that experiences migration, the merging of two separate populations can result in non-random mating, leading to observed allelic and genotypic frequencies that deviate from what is predicted by the Hardy-Weinberg equilibrium. This is because the new population may consist of individuals from different subpopulations with different genetic backgrounds and mating preferences, which can lead to mating patterns that are not random. As a result, some combinations of alleles may become more or less frequent in the new population, leading to changes in the observed genotype frequencies.

Question 18

What is the ultimate source of all genetic variability?

Accepted Answer

The ultimate source of all genetic variability is mutation, which is the sudden change in the DNA sequence that can create new alleles. Natural selection and artificial selection act on this variability, but they do not create it. Therefore, options A, B, and D are incorrect. Option E is also incorrect because without genetic variability, evolutionary change would not be possible.

Question 19

How does random genetic drift affect large populations?

Accepted Answer

Random genetic drift has very little effect on large populations because there is a much smaller chance of a random event drastically affecting the entire population. The larger the population, the more likely it is that natural selection will be the primary evolutionary force.

Question 20

Which type of selection can affect the distribution of a quantitative trait?

Accepted Answer

All of these types of selection can affect the distribution of a quantitative trait. Directional selection favors one extreme of the trait distribution, potentially shifting the entire distribution over time. Disruptive selection favors both extremes of the trait distribution, potentially leading to a bimodal distribution. Stabilizing selection favors the mean of the trait distribution, reducing variation and making the distribution more narrow.

Quiz 23: Population Genetics

What general effect does random genetic drift have on populations? 1) It reduces the dominant homozygosity. 2) It reduces the heterozgosity. 3) It reduces the recessive homozygosity.