Genetic Ch. 23

Which of the following are required for gene flow to occur?

- Migrants must be fertile and pass their genes to the next generation. - Individuals must migrate from one population to another.

Which of the following are likely reasons for differences in the reproductive success of different genotypes in a population?

- Some genotypes are more likely to find mates than others. - Some genotypes are more fertile than others. - Some genotypes are more likely to survive to reproductive age than others.

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.

- There is 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 population of small insects consists of 500,000 individuals. The mutation rate for a gene in this species is 0.00001 mutations per gene per generation. What is the expected number of new mutations in this population in the next generation?

10

A population is undergoing a directional selection for a gene with two alleles, allele A has a frequency of 0.4, and allele a has a frequency of 0.6. The relative fitness values for the three genotypes are as follows: wAA = 1, wAa = 0.5, and waa = 0.5. What would be the expected frequencies of the two alleles after one generation?

A - 0.48; a - 0.52

If genetic drift is followed over a great many generations, what is its expected effect on allele frequencies?

Alleles are either lost (frequency of 0%) or fixed (frequency of 100%) in the populations.

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.

Which of the following formulas allows us to calculate the expected number of mutations in a gene in a population? (Let N = number of individuals in the population and μ = mutation rate)

Expected number of new mutations = 2Nμ

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

Gene Pool

Two types of factors can govern microevolution. On one hand, mutation is a constant source of new genetic variation. On the other hand, mechanisms that alter existing genetic variation, such as natural selection and genetic drift, can act to alter existing genetic variation. How do those two types of factors compare in terms of the magnitude of their effect on allele frequencies in a population?

Mutations have a negligible effect on allelic frequencies, while mechanisms such as natural selection and drift can have a dramatic effect.

Which of the following would not be true for a population that is in Hardy-Weinberg equilibrium for a specific gene?

Natural selection favors individuals with a heterozygous genotype.

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

The field that studies the extent of genetic variation within groups of people over time is called

Population genetic

Mutations occur when the DNA of an organism changes. Changes often happen in gene , but may also involve the structure and number of chromosomes.

Sequences

What does the selection coefficient measure?

The extent to which a genotype is selected against

The weight of a human baby at birth is a quantitative trait determined by the activity of many genes. Babies with very low or very high birth weights have a decreased chance of survival, while babies with intermediate birth weights have much better chances of survival. What can you hypothesize about the genetic diversity of genes that determine birth weight in humans?

They are under stabilizing selection, which should decrease their genetic diversity.

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.

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 every gene that were passed from the 60 parents to the 48 new cubs

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

allele; p allele

Why are repetitive sequences, such as microsatellites and minisatellites, an extremely useful tool for studying population genetics?

because they tend to exhibit considerable variation between individuals

According to the principles of natural selection, a mutant allele will increase in the population if it is ______ to reproduction and survival.

beneficial

Population genetics is a field that is concerned with ______.

changes in genetic variation within a group of individuals over time.

In a specific population, a gene is present as two alleles: D and d. For every 100 dd individuals that survive to reproduce, 18 DD and 99 Dd individuals survive to reproduce as well. Which of these three genotypes has the highest Darwinian fitness and what is its value (w)? Assume that all individuals that survive to reproduce have roughly the same number of offspring.

dd, wdd = 1.0

If a high chi square value is obtained when comparing observed and expected genotypes in a population, we can state 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 ______ over the course of many generations.

do not change

Any random change in the frequencies of alleles in a population is referred to as genetic

drift

A population that has experienced a bottleneck is highly susceptible to genetic drift ______.

during the initial bottleneck and during the generations following the bottleneck when the population size is small

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.

A group of individuals from a larger population can migrate to a new area and establish a colony, which will be highly susceptible to genetic drift. This is known as the ______ effect.

founder

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

gametes are formed from alleles independently chosen at random from

The transfer of genetic material from one species to another (regardless of the exact mechanism) is called ______.

horizontal gene transfer

Which of the following phenomena is responsible for introducing new genetic variation in a population?

mutation

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

p2 + 2pq + q2 = 1

A group of individuals of the same species, which occupy the same region, and can successfully interbreed with each other, is a(n) _________ of that sexually reproducing species.

population

Which of the following formulas describe the situation in which a population undergoing balancing selection due to heterozygote advantage reaches equilibrium? In this case, we have a single gene, with two alleles, B and b, with frequencies of p (for the B allele) and q (for the b allele).

sBBp = sbbq

Microevolution is best described as

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

Balancing selection favors ______.

the maintenance of two or more alleles in a population

Which of the following would be a neutral mutation?

- mutation of a sequence within an intron - change in the wobble position without affecting the amino acid sequence of the encoded protein - missense mutation that causes an amino acid substitution which does not affect the proper folding of the protein

Consider two populations of the same species and a gene that is found in two alleles in both populations (alleles D and d). Choose all values that need to be known in order to calculate the change in the frequency of the allele D if some individuals migrate from one of the populations into the other.

- proportion of the conglomerate population that is due to migrants from the donor population - frequency of D in the original recipient population - frequency of D in the donor population

A specific gene is found in two forms in a population, D and d, with frequencies of 0.6 and 0.4, respectively. The D allele can mutate into the d allele at a rate of 0.00001 mutations per gene per generation. What would the expected frequency of the d allele be after one generation? Assume that the reverse mutation d to Ddoes not occur.

0.400006

Which of the following is a typical mutation rate (with proper units) for a gene in a natural population?

10−6 per gene per generation

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

Darwinian fitness

New mutations can be deleterious, neutral, or beneficial. Which of those three general types of mutations are most likely to occur?

Deleterious and neutral mutations are much more likely than beneficial mutations.

Individuals at one extreme of a phenotypic distribution are more likely to survive and reproduce in a particular environment due to ________ selection.

Directional

The mean fitness of a population undergoing directional selection is ______.

Less than 1

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.

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 ______ frequency of the ______.

genotype; DD genotype

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

the relative likelihood that a genotype will contribute alleles to the next generation as compared to other genotypes