Chapter 27

Population genetics is concerned with the

- Extent of genetic variation within a group of individuals

Consider a population of cheetahs, inhabiting a protected area in Africa. In 2012, there were 112 cheetahs in this population. During that year, 60 of those animals reproduced and 48 new cubs were born. What constitutes the gene pool of the new generation made of those 48 new cubs?

-All of the alleles of all the genes that were passed from the 60 parents to the 48 new cubs

Consider a population of a hypothetical animal, whose fur color is determined by a single gene, called Col. From the list below choose all conditions that must be met in order for this population to be in Hardy-Weinberg equilibrium for the Col gene.

-No natural selection -Animals in the population mate randomly, regardless of their genotype for the Col gene -No new mutations in the Col gene

A gene is found in two forms in a population of plants. The two alleles are denoted as B, and b. You determine that the frequency of the B allele in this population is 0.2. If this population was in a Hardy-Weinberg equilibrium, calculate the probability of a heterozygote in the next generation.

.32

You are studying a bird population and a gene that has 2 alleles, A, which is found at a frequency of 0.4, and a, which is found at a frequency of 0.6. If this population was in Hardy-Weinberg equilibrium, what would be the probability of the genotype aa in the next generation?

0.36

Consider a population, for which you know the allele composition of three genes. Gene A has three alleles in the following proportions: A1 - 34.4%, A2 - 30%, A3 - 35.6%. Gene B has two alleles in the following proportions: B1 - 67.1%, B2 - 32.9%. Gene C has two alleles in the following proportions: C1 - 99.2%, C2 - 0.8%. Which of those genes is(are) polymorphic?

A and B only

Which of the following correctly defines a population of sexually reproducing species for the purposes of population genetics?

A group of individuals that occupy the same area and can interbreed with each other

Which of the following is a situation in which directional selection may be observed

A new allele, which promotes higher fitness in organisms that carry it, is introduced in a population (for example, by a random mutation)

Which of the following best describes the relationship between a genotype's fitness and its frequency in negative frequency-dependent selection?

As the frequency of a genotype increases, its fitness decreases.

The relative (compared to other genotypes) likelihood that a genotype will contribute its alleles to the next generation is known as

Darwinian fitness

In ___ selection, individuals at one extreme of a phenotypic distribution are more likely to survive and reproduce in a particular environment.

Directional

Sometimes individuals at one extreme of a phenotypic distribution are favored in a particular environment, for example, selection will strongly favor insects that have very high resistance to an insecticide. In such cases, the type of selection that operates is

Directional Selection

You are studying a population of birds that has recently become established on an island some 1,000 km from the mainland. On the mainland, these birds mostly consume fleshy fruits, however, on the island they are forced to eat nuts that have to be cracked open with a strong beak. What type of selection is most likely to occur for genes that determine the size and strength of the beak in these birds?

Directional selection

The change in a population's gene pool from one generation to the next is known as

Microevolution

How is the allele frequency of a population calculated?

The number of copies of the allele in the population is divided by the total number of all the alleles for the same gene in the population.

How can we calculate the frequency of a specific genotype in a population?

The number of individuals with this genotype in the population is divided by the total number of individuals in the population.

Which of the following is the best definition of Darwinian fitness as it relates to population genetics

The relative (compared to other genotypes) likelihood that a genotype will contribute alleles to the next generation

In certain populations, natural selection can favor the maintenance of 2 or more alleles in a population. An example of this is ______ selection

balancing

A population would be described as being in ______ if a high chi-square value is obtained when testing whether the allele and genotype frequencies are in Hardy-Weinberg equilibrium.

disequilibrium

When the hypothesis that the allele and genotype frequencies are in Hardy-Weinberg equilibrium is rejected, it can be stated that the population is in

disequilibrium

The Hardy-Weinberg equilibrium is a mathematical expression which predicts that, when certain requirements are met, the allele and genotype frequencies of a gene in a population

do not change over the course of many generations

In order to derive the Hardy-Weinberg equation, the two scientists assumed that ______ population's gene pool.

gametes are independently chosen at random from the population's gene pool

The ___ ___ of a population consists of all of the alleles of every gene in all of the individuals of that population.

gene pool

Consider a population and a gene that has two alleles in this population, designated as D and d. If you divide the number of individuals with the genotype DD by the total number of individuals in the population, you will calculate the

genotype frequency of the DD genotype

Which of the following is an accurate depiction of the Hardy-Weinberg equation for a gene with two alleles?

p2 + 2pq + q2 = 1

In population genetics, a gene that exists as two or more alleles in a population is a(n) ______ gene, while one that exists predominantly as a single allele is a(n) ______ gene.

polymorphic; monomorphic

Most of the traits in a healthy natural population exhibit some level of variation, or ___, that is, they are found in two or more forms.

polymorphism

When scientists study populations, they typically observe high levels of variation in many of the traits that characterize a species. In genetics, variations in traits at the population level are known as

polymorphisms.

The genetics field that is concerned with the extent of genetic variation within a group of individuals and changes in that variation over time is

population

Microevolution is best described as

the change in a population's gene pool from generation to generation

Which of the following (choose all that apply) are conditions that must be met in order for a population to be in Hardy-Weinberg equilibrium for a specific gene of interest?

-No new mutations should be appearing in the gene of interest. -All of the different genotypes (with respect to the gene of interest) must have equal reproductive success (no selection). -The population must be large enough so that no genetic drift is occurring.

Which of the following best explains the high prevalence of the HbS allele of the human β-globin gene in populations living in areas of high malaria prevalence?

This gene is under balancing selection due to heterozygote advantage in those areas

The Hardy -Weinberg equilibrium is used as a null hypothesis, i.e., if a population is in Hardy-Weinberg equilibrium, then

evolutionary change is not occurring in this population

According to the theory of ____ ____, individuals with alleles leading to greater reproductive success will be more likely to produce offspring and pass those alleles to the next generation.

natural selection

Natural selection is the phenomenon in which certain phenotypes have ______ than other phenotypes.

greater reproductive success

In genetics, a ___ of a sexually reproducing species consists of a group of individuals of that species, which occupy the same region, and can successfully interbreed with each other.

Population

Consider a population and a gene that has two alleles in this population, designated as E and e. If you divide the number of all the copies of the e allele in the population by the total number of copies of both alleles (E and e) in the population, you will calculate the

allele frequency of the e allele

The ______ of a population is the sum of the frequencies of all genotypes, each one multiplied by its respective relative fitness.

mean fitness