Chapter 23: Population Genetics (Book Questions) Flashcards
The study of genes and genotypes in a population is called ___________ ___________
Population genetics
The _________ __________ of a population consists of all of the alleles for every gene in the population.
Gene pool
In a population, only individuals who ________ contribute to the gene pool of the next generation.
reproduce, breed, or procreate
Geographic isolation can divide a species into discrete populations because ______.
Multiple choice question.
it prevents natural selection from acting on the populations
it prevents the populations from exchanging alleles
it causes different mutations to occur in the separated populations
it prevents the populations from exchanging alleles
Some genetic changes make some individuals in a population become better suited to their environment and therefore more likely to survive and reproduce. This phenomenon is termed __________.
adaptation
What term refers to the presence of two or more variants for a given character in a population?
Multiple choice question.
Adaptation
Equilibrium
Polymorphism
Mutation
Polymorphism
If 99% or more of its alleles are identical, a gene is said to be ______; and it is ____________ if at least two alleles occur at a frequency greater than 1%.
monomorphic; polymorphic
The number of copies of an allele in a population divided by the total number of all alleles for that gene in a population is the ______.
Multiple choice question.
allele frequency
genotype frequency
frequency of heterozygosity
SNP frequency
allele frequency
The genotype frequency is calculated by dividing the number of individuals in a population who have a particular ______ by the total number of ______ in that population.
Multiple choice question.
genotype; individuals
genotype; genotypes
allele; genotypes
allele; alleles
genotype; individuals
If a population of mammals moves from a warm geographic location to a colder geographic location, individuals with a(n) ______ such as thicker fur might be more likely to survive and reproduce in the new environment due to ______.
Multiple choice question.
vestigial structure; natural selection
adaptation; natural selection
adaptation; artificial selection
vestigial structure; artificial selection
adaptation; natural selection
The frequency at which homozygotes and heterozygotes occur within a population can be described by ______.
Multiple choice question.
genotype frequencies
relative fitness of a genotype
allele frequencies
SNP frequency per gene
genotype frequencies
The reason why allele frequencies is not the right answer is because allele frequencies describe the frequencies of individual alleles (e.g., A or a). Genotype frequencies describe the frequencies with with combinations of alleles, or genotypes, occur (e.g., AA, Aa, or aa).
In four-o’clock plants, flowers with the genotype CRCR are red, flowers with the genotype CRCW are pink, and flowers with the genotype CWCW are white. A population of four-o’clocks consists of 30 plants with red flowers, 10 plants with pink flowers, and 60 plants with white flowers. What is the frequency of the CR allele in this population?
Multiple choice question.
- 65
- 20
- 70
- 35
0.35
Ooooo
For the first part of the equation, you need to count all instances of Cr… That means, 10 + 60 because CRCR has two of the alleles in question.
10 + 30 + 30 = 70
Divided by the total amount of alleles in the population
(30 x 2) + (10 x 2) + (60 x 2) = 200
70/200 = .35
In a diploid species, how many copies of a given allele are present in an individual who is heterozygous for the gene?
Multiple choice question.
2
0
4
1
1
Not two because a heterozygote has two copies of the genes, bot only one copy of each allele.
The allele frequency is calculated by dividing the number of copies of a specific ______ in a population by the ______ for that gene in that population.
Multiple choice question.
genotype; total number of individuals
allele; total number of individuals
allele; total number of all alleles
genotype; total number of all genotypes
allele; total number of all alleles
In radishes, genotype RR is red, genotype Rr is purple, and genotype rr is white. In a population of radishes consisting of 100 red radishes, 100 purple radishes, and 300 white radishes, what is the frequency of the genotype rr?
Multiple choice question.
- 33
- 25
- 70
- 60
0.60
The number of individuals with a particular genotype in a population divided by the total number of individuals in a population is the ______.
Multiple choice question.
polymorphism frequency
Hardy-Weinberg equilibrium
allele frequency
genotype frequency
genotype frequency
Consider a population of 100 four o’clock flowers. In this population, 55 flowers are red and have the genotype CRCR, 20 flowers are pink and have the genotype CRCW, and 25 flowers are white with the genotype CWCW. The frequency of the CR allele in this population is ________%.
65
Consider a population of flowers in which the genotype CRCR produces red flowers, CRCW produces pink flowers, and CWCW produces white flowers. If the frequency of the CR allele is 0.2 and the frequency of the CW allele is 0.8, what is the frequency of the red flower genotype?
- 40
- 20
- 32
- 04
.04
The frequency of the homozygous genotype, CRCR, when the frequency of allele is known; just square the allele frequency in question.
.2 x .2 or .2^2 = .04
A diploid homozygous individual has ______ copies of the given allele.
Multiple choice question.
0
4
2
1
2
A particular gene segregates two alleles, and the dominant allele has a frequency of 0.9. What is the frequency of the recessive allele?
Multiple choice question.
- 3
- 9
- 5
- 1
0.1
Remember: p + q = 1
This can be used if one allele frequency is known.
The Hardy-Weinberg equation states for a gene exists in two alleles and the genotypes can be found.
The MN blood group in humans is determined by two alleles of a single gene. In a population containing 90 individuals with genotype MM and blood group M, 80 individuals with genotype MN and blood group MN, and 30 individuals with genotype NN and blood group N, what is the frequency of the genotype MN?
Multiple choice question.
- 40
- 80
- 70
- 65
.40
90 = MM genotype
80 = MN genotype
30 = NN genotype
A student proposes that left-handedness is a recessive trait. A survey of a class of 36 students finds that 27 (0.75) are right-handed and 9 (0.25) are left-handed. If this population is in Hardy-Weinberg equilibrium, what are the genotypic and allele frequencies?
Multiple choice question.
- 75 homozygous dominant and 0.25 homozygous recessive, and a 3-to-1, right-to-left handed allele ratio in the population
- 25 homozygous dominant, 0.50 heterozygous, and 0.25 homozygous recessive, and a 0.5 allele frequency for each allele
- 50 homozygous dominant, 0.25 heterozygous, and 0.25 homozygous recessive, and a 0.5 allele frequency for each allele
They cannot be estimated using these limited data.
p^2 + 2pq + q^2 = 1
p + q = 1 (.75 + .25 = 1)
Reason: The frequency of left-handed individuals represents q2 in the Hardy-Weinberg equation. Taking the square root of 0.25 = 0.5 = q. Since p + q = 1, p = 0.5. Then use the equation to find the frequencies of the genotypes.
Correct Answer: 0.25 homozygous dominant, 0.50 heterozygous, and 0.25 homozygous recessive, and a 0.5 allele frequency for each allele
Consider a gene that segregates two alleles, A and a, with allele frequencies given by p and q, respectively. The frequency of the aa genotype will be ______ if the population is in Hardy-Weinberg equilibrium.
q2
2pq
p2
pq
q
q2
Reason: No. 2pq is the expected frequency of the Aa genotype.
Reason: No. p2 is the expected frequency of the AA genotype.
Reason: No. q is the frequency of the a allele. The aa genotype has two a alleles, so its frequency is q X q, or q2.
Suppose plants with the genotype FRFR produce red flowers, plants with the genotype FRFW produce pink flowers, and plants with the genotype FWFW produce white flowers. If the frequency of the FR allele is 0.2 and the frequency of the FW allele is 0.8, what is the frequency of pink flowers?
Multiple choice question.
- 50
- 32
- 04
- 16
0.32
For a gene with two alleles, S and s, if the frequency of the one allele (S) is 0.25, then the frequency of the other allele (s) is _________ .
.75
The Hardy-Weinberg equation assumes that ______.
Multiple choice question.
homozygotes occur more commonly than heterozygotes
the frequencies of the two homozygotes are the same
gametes combine randomly to produce offspring
heterozygotes result when gametes combine selectively
gametes combine randomly to produce offspring
In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.4. What is the percentage of the population that is homozygous for this allele?
Multiple choice question.
40
32
4
16
q^2 = .16 or 16%
The frequency of a gamete carrying a particular allele is the same as ______.
Multiple choice question.
the allele frequency in the population
the genotype frequency in the population
the number of copies of that particular allele in a population
the total number of alleles in the population
the allele frequency in the population
Consider a gene with two alleles, A and a, that occur in a population with the frequencies 0.8 and 0.2, respectively. If the population is in Hardy-Weinberg equilibrium, what genotype frequencies will be observed?
Multiple choice question.
- 64 AA, 0.32 Aa, and 0.04 aa
- 25 AA, 0.50 Aa, and 0.25 aa
- 80 AA and 0.20 aa
- 80 AA, 0.16 Aa, and 0.04 aa
0.64 AA, 0.32 Aa, and 0.04 aa
In pea plants, a gene with two alleles determines whether the flowers are purple or white. If the frequency of the allele for purple flowers is 0.55 and the frequency of the allele for white flowers is 0.45, the frequency of gametes carrying the purple flower allele will be ________.
55%
Select all that apply
Select the conditions that must be met for a population to be in Hardy-Weinberg equilibrium.
Multiple select question.
The population is very large.
Mating is random.
Evolution is occurring.
Natural selection is not occurring.
Migration occurs frequently.
The population is very large.
Mating is random.
Natural selection is not occurring.
What conclusion can be drawn from the observation that a population is not in Hardy-Weinberg equilibrium?
Multiple choice question.
Evolutionary forces are affecting the population.
Mechanisms of evolutionary change are not affecting the population.
Allele frequencies are stable from one generation to the next.
The population is likely to disappear because it is not adapted to its environment.
Evolutionary forces are affecting the population.
Select all that apply
Which of the following are sources of new genetic variation?
Multiple select question.
Natural selection
Genetic drift
Gene duplication
Random mutation
Horizontal gene transfer
Gene duplication
Random mutation
Horizontal gene transfer
If the Hardy-Weinberg equilibrium is met, what is indicated?
Multiple choice question.
Evolution leading to a population better adapted to the environment is occurring.
Evolution is not occurring because the alleles in the population remain the same.
The population does not satisfy the assumptions of the Hardy-Weinberg equation.
Very slow and continuous evolution is occurring with no increased adaptation.
Evolution is not occurring because the alleles in the population remain the same.
There are several sources of new genetic variation in a population. New alleles of pre-existing genes can arise by random _____, and new genes can be introduced into a population by gene ________, and _________ gene transfer
mutation, duplication, horizontal
Select all that apply
Which factors can cause microevolution to happen?
Multiple select question.
Two populations evolve the same trait and exhibit molecular homology.
Evolutionary forces change allele frequencies from one generation to the next.
Hardy-Weinberg equilibrium is achieved.
New genetic variation is introduced into a population.
Evolutionary forces change allele frequencies from one generation to the next.
New genetic variation is introduced into a population.
What is reproductive success?
Multiple choice question.
The likelihood that a sperm can fertilize an egg
The likelihood of contributing fertile offspring to the next generation
The likelihood of finding a suitable mate
The likelihood of being selected by a potential mate
The likelihood of contributing fertile offspring to the next generation
Which type of selection favors individuals at one extreme of a phenotypic range who have greater reproductive success in a particular environment?
Multiple choice question.
Stabilizing selection
Balancing selection
Directional selection
Diversifying selection
Directional selection
What process explains how beneficial alleles that are heritable become more common in successive generations?
Multiple choice question.
Migration
Genetic drift
Natural selection
Evolution
Heritability
Natural selection
Sexual selection can lead to a significant difference in appearance between the two sexes. What is this called?
Multiple choice question.
Balanced fitness
A balanced polymorphism
A sex-linked trait
Intersexual fitness
Sexual dimorphism
Sexual dimorphism
The term “genetic drift” refers to the fact that allele frequencies tend to “drift” ______ from generation to generation due to chance.
Multiple choice question.
in a balanced way
toward common traits
randomly
toward beneficial traits
randomly
Genetic drift selects for ______.
Multiple choice question.
alleles with intermediate fitness
alleles with the highest fitness
no particular allele
alleles with the lowest fitness
no particular allele
During _______ selection, individuals at one extreme of a phenotypic range have greater reproductive success in a particular environment.
directional
A dramatic reduction in population size due to a natural disaster or destruction of habitat and the resulting change in the allele frequencies of the new population is called ______.
Multiple choice question.
directional selection
the founder effect
negative frequency-dependent selection
the bottleneck effect
the bottleneck effect
A change in allele frequencies due to genetic drift in a population that colonized a new location is called ______.
Multiple choice question.
the bottleneck effect
disruptive selection
balancing selection
gene flow
the founder effect
the founder effect
How does genetic drift affect allele frequencies in a population?
Multiple choice question.
It eliminates deleterious alleles from the population.
It eliminates advantageous alleles from the population.
It maintains alleles in a balanced polymorphism.
It changes allele frequencies without regard for their fitness.
It changes allele frequencies without regard for their fitness.
Genetic drift can promote _________ variation, which are changes in genes and proteins that do not affect reproductive success.
neutral
What statement best describes assortative mating?
Multiple choice question.
Individuals mate based on female preference of showy characteristics in males.
Individuals with similar phenotypes are more likely to mate.
Individuals with dissimilar phenotypes are more likely to mate.
Individuals mate without regard for their genotypes or phenotypes.
Individuals with similar phenotypes are more likely to mate.
Neutral variation describes changes in genes and proteins that do not affect ______.
Multiple choice question.
reproductive success
visible phenotypes
heritable traits
reproductive success
