Chapter 27: Population Genetics

Usually, the allele frequencies in the founding population are very different from those of the original population.

A founding population usually has lower genetic diversity than the original population it came from. For those alleles that are shared by the two populations, how are allele frequencies different (or similar)?

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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.

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A gene is present in the form of three alleles in a population, G, g1, and g2. If the frequency of the G allele is 0.6, and the frequency of the g1 allele is 0.2, then what is the frequency of the g2 allele?

founder

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.

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

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

disequilibrium

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.

The Michigan population likely experienced a bottleneck in the past. Both populations are equally susceptible to genetic drift.

A scientist is studying two populations of the same species of birds - one in Michigan and one in Montana. Both populations are relatively large (with more than 10,000 individuals each). However, the Michigan population has a much lower genetic diversity than the Montana population. Which of the two populations is most likely to have experienced a bottleneck and which of the two populations is currently more susceptible to genetic drift?

natural selection

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.

exons

By looking at many different proteins and the genes that encode them in a variety of eukaryotic organisms, scientists have determined that a protein domain tends to be encoded by one or a few (usually adjacent) .

The founding population typically has less genetic diversity than the original population. The founding population typically has very different allele frequencies from those of the original population.

Choose the two most important results of the founder effect on the newly founded population.

allele frequency of the e allele

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 ______.

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

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?

heterozygote advantage

Consider a single gene with two alleles in a population of wild birds. A situation in which the heterozygotes for that gene have higher fitness than the two homozygote genotypes is known as _______________ _________________. In these situations, an equilibrium is reached, in which both alleles of the gene are maintained in the population.

A, B, and C

Consider the following types of changes in DNA: a deletion of part of a gene (A); a duplication of a region in a gene (B); a replacement of one nucleotide with a different one (C). Which of those changes can cause polymorphisms in a population?

horizontal

During _________________ gene transfer, genetic material from a donor organism is incorporated into a recipient organism which is not the donor's offspring.

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

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

fingerprinting

In DNA ______________________, an individual is characterized based on the repetitive sequences in his or her genome.

balancing

In __________ selection, natural selection favors the maintenance of two or more alleles in a population. An example of that is the phenomenon of heterozygote advantage.

directional

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

balancing

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

two or more alleles are maintained in a heterogeneous environment

In disruptive selection, ______.

population

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.

gametes are independently chosen at random from the

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

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

Microevolution is best described as ______.

polymorphism

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.

sequences

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

Genetic drift is random, so deleterious, beneficial, or neutral alleles can become fixed.

Over time, genetic drift can lead to the fixation of an allele. What types of alleles are usually fixed by drift?

extent of genetic variation within a group of individuals

Population genetics is concerned with the ______.

A few to a few thousand base pairs

Repetitive sequences are composed of a certain sequence that is repeated many times throughout the genome of a species. What is the typical size of the sequence that is being repeated?

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 ______ selection.

founder

Sometimes populations become susceptible to genetic drift via the___________________ effect. This happens when a small group of individuals separates from a larger population and migrates to a different site, where it establishes a colony.

evolutionary change is not occurring in this population

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

do not change over the course of many generations

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 ______.

gene pool

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

bottleneck

The _______________effect is observed when a population's size is dramatically reduced due to natural events, such as earthquakes and flood, or due to human destruction of habitat.

microevolution

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

population

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 ________________ genetics.

gene flow

When individuals migrate, alleles can be transfered from one population to another population. This commonly referred to as __________ ________________.

polymorphisms

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 ______.

heterozygote advantage

When the heterozygotes for a specific gene have higher fitness than either of the corresponding homozygous genotypes (assume a single gene with two alleles), we are observing a situation called ______.

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 _____________.

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

Which are required for gene flow to occur?

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

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

10-6 per gene per generation

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

p2 + 2pq + q2 = 1

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

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

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

DNA fingerprinting

Which technique characterizes human individuals by analyzing the presence and sizes of repetitive sequences in their DNA?

Disruptive selection

Which type of selection is also known as diversifying selection because it tends to favor the survival of two or more different phenotypes in a heterogeneous environment?

Stabilizing selection

Which type of selection tends to select against extreme phenotypes for a quantitative trait, because individuals with intermediate phenotypes have the highest relative fitness values?

Population 1 is more susceptible.

You are observing two populations of the same animal species. Population 1 consists of 46 individuals, while population 2 consists of 3325 individuals. Which population is more susceptible to genetic drift?

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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?

Stabilizing

__________________selection acts on quantitative traits determined by multiple genes. In this type of selection, individuals with intermediate phenotypes have higher fitness and are selected for, while extreme phenotypes are selected against.

mutation

A ________________is any change in the DNA of an organism, for example, a change in DNA sequence or the structure and number of chromosomes.

single polymorphism

A change in one nucleotide in a gene is also known as a____________ -nucleotide ___________, or, SNP.

random change of allele frequencies

Genetic drift is the _____ in a population.

Each protein domain tends to be encoded by a single exon, or in some cases a few, adjacent exons.

How is a protein domain related to the exons of a gene?

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 is the allele frequency of a population calculated?

greater reproductive success

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

rate

The probability that a gene will be altered as a result of mutation is known as the mutation ___________.

Darwinian fitness

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

100%

The sum of the frequencies of all of the alleles of a particular gene in a population is always __________.

drift

The term ______________genetic refers to any random change in the frequencies of alleles in a population.

horizontal gene transfer

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