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Genetics > Chapter 27 - Population Genetics > Flashcards

Chapter 27 - Population Genetics Flashcards

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1
Q

This field of genetics is concerned with genetic variation, its extent within populations, and how it changes over many generations

A

Population genetics

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2
Q

When did population genetics emerge as a branch of genetics?

A

1920s/1930s

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3
Q

The foundations of population genetics are largely attributed to these three mathematicians

A

Sir Ronald Fisher, Sewall Wright and J. B. S. Haldane

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4
Q

All of the alleles of every gene in a population make up this

A

Gene pool

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5
Q

Only these individuals contribute to the gene pool of the next generation

A

Individuals that reproduce

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6
Q

This is a group of individuals of the same species that occupy the same region and can interbreed with each other

A

Population

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7
Q

A large population is usually composed of these smaller groups

A

Local populations

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8
Q

Local populations are often separated from each other by these

A

Moderate geographic barriers

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9
Q

A population may change in these three ways

A

Size, geographic location and genetic composition

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10
Q

This term describes a gene that commonly exists as two or more alleles in a population

A

Polymorphic

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11
Q

This term describes a gene that exists predominantly as a single allele

A

Monomorphic

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12
Q

When a single allele is found in at least this percentage of cases in a population, it is considered monomorphic

A

99%

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13
Q

Genetic variation is often this, a change in a single base pair in the DNA

A

Single-nucleotide polymorphism (SNP)

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14
Q

SNPs account for this percentage of variation among people

A

90%

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15
Q

In humans, a gene that is 2,000 to 3,000 base pairs contains this many different polymorphic sites on average

A

10

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16
Q

What is the formula for allele frequency?

A

Allele frequency = Number of copies of an allele in a population / Total number of alleles for that gene in a population

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17
Q

What is the formula for genotype frequency in a population?

A

Genotype frequency = Number of individuals with a particular genotype in a population / Total number of individuals in a population

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18
Q

For a given trait, the allele and genotype frequencies are always less than or equal to this number

A

1 (or 100%)

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19
Q

What will the allele frequency be for a monomorphic gene in a population?

A

Equal or close to 1

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20
Q

For polymorphic genes in a population, the frequencies of all alleles should add up to this number

A

1

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21
Q

This equation was formed independently by Godfrey Harold Hardy and Wilhelm Weinberg in 1908 to relate allele and genotype frequencies in a population

A

Hardy-Weinberg equation

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22
Q

The Hardy-Weinberg equation states that, under a given set of conditions, allele and genotype frequencies do this

A

Remain unchanged over many generations

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23
Q

What are the five conditions that make the Hardy-Weinberg equation true for allele frequencies in a population?

A
  1. No new mutations; 2. No genetic drift; 3. No migration; 4. No natural selection; 5. Random mating
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24
Q

In reality, does any population completely satisfy the conditions of the Hardy-Weinberg equation?

A

No

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25
Q

These populations can nearly approximate Hardy-Weinberg equilibrium for certain genes

A

Large populations

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26
Q

What is the formula for the Hardy-Weinberg equation?

A

p^2 + 2pq + q^2 = 1

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27
Q

This statistical test can be used to see if a population really exhibits Hardy-Weinberg equilibrium for a particular gene

A

Chi square test

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28
Q

If the null hypothesis is not rejected after using a chi square test to see if a population is in Hardy-Weinberg equilibrium, is the population in equilibrium for a particular gene?

A

Yes

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29
Q

If the null hypothesis is rejected after using a chi square test to determine if a population is in Hardy-Weinberg equilibrium, is the population in equilibrium for a particular gene?

A

No

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30
Q

This describes changes in a population’s gene pool from generation to generation

A

Microevolution

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31
Q

What is the source of new genetic variation in populations?

A

Mutation

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32
Q

What are four mechanisms that alter existing genetic variation in populations?

A

Natural selection, genetic drift, migration, nonrandom mating

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33
Q

In the 1850s, these two scientists independently proposed the theory of natural selection

A

Charles Darwin and Alfred Russel Wallace

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34
Q

According to the theory of natural selection, phenotypes may vary with regard to this

A

Their reproductive success

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35
Q

This is the relative likelihood that a genotype will survive and contribute to the gene pool of the next generation

A

Darwinian fitness

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36
Q

A gene with two alleles, A and a, will have three genotypic classes that can be assigned these according to their reproductive success

A

Relative fitness values (w)

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37
Q

By convention, the gene with the highest reproductive ability is given this fitness value

A

1

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38
Q

What are three reasons why there could be differences in reproductive achievement for different genotypes?

A
  1. Fittest genotype is more likely to survive; 2. Fittest genotype is more likely to mate; 3. Fittest genotype is more fertile
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39
Q

What are the four patterns of natural selection?

A
  1. Directional selection; 2. Balancing selection; 3. Disruptive (or diversifying selection); 4. Stabilizing selection
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40
Q

This type of natural selection favors the survival of one extreme phenotype that is better adapted to an environmental condition

A

Directional selection

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41
Q

This type of natural selection favors the maintenance of two or more alleles

A

Balancing selection

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42
Q

This type of natural selection favors the survival of two (or more) different phenotypes

A

Disruptive (or diversifying selection)

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43
Q

This type of natural selection favors the survival of individuals with intermediate phenotypes

A

Stabilizing selection

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44
Q

Does the value for the mean fitness of the population have to add up to 1?

A

No

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45
Q

Which genotype (heterozygote or homozygote) has an advantage in balancing selection?

A

Heterozygote

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46
Q

This measures the degree to which a genotype is selected against

A

Selection coefficient

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47
Q

What is the formula for selection coefficient?

A

s = 1 - w

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48
Q

Heterozygote advantage can sometimes explain the high frequency of these alleles

A

Deleterious alleles

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49
Q

This is another mechanism of balancing selection in which rare individuals have a higher fitness than more common individuals

A

Negative frequency-dependent selection

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50
Q

Does disruptive selection typically act on traits that are determined by one gene or by multiple genes?

A

Multiple genes

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51
Q

Disruptive selection is likely to occur in populations that occupy these environments

A

Diverse environments

52
Q

Does stabilizing selection tend to increase or decrease genetic diversity?

A

Decrease

53
Q

Since 1973, these two scientists have studied natural selection in finches on the Galapagos Islands

A

Peter and Rosemary Grant

54
Q

This refers to random changes in allele frequencies due to random fluctuations

A

Genetic drift

55
Q

This scientist played a key role in developing the concept of genetic drift in the 1930s

A

Sewall Wright

56
Q

What are two important consequences of the founder effect?

A
  1. Founding population expected to have less genetic variation than original population; 2. Founding population will have allelic frequencies that may differ markedly from those of original population as a matter of chance
57
Q

This is the transfer of alleles from a donor population to a recipient population, changing its gene pool

A

Gene flow

58
Q

After gene flow, the new population that forms is called this

A

Conglomerate

59
Q

To calculate allele frequencies in a conglomerate, these two things must be known

A
  1. Original allele frequencies in donor and recipient populations; 2. Proportion of conglomerate population that is due to migrants
60
Q

What is the calculation for change in allele frequency for a conglomerate population?

A

Δp_c = m(p_D − p_R)

61
Q

What does Δp_c stand for in calculating allele frequency changes in conglomerate populations?

A

Change in allele frequency in the conglomerate population

62
Q

What does p_D stand for in calculating allele frequency changes in conglomerate populations?

A

Allele frequency in donor population

63
Q

What does p_R stand for in calculating allele frequency changes in conglomerate populations?

A

Allele frequency in original recipient population

64
Q

What does m stand for in calculating allele frequency changes in conglomerate populations?

A

Proportion of migrants in the conglomerate population

65
Q

What is the calculation for finding m (the proportion of migrants in the conglomerate population)?

A

m = Number of migrants in conglomerate population / Total number of individuals in conglomerate population

66
Q

What are two important consequences of bidirectional migration?

A
  1. It tends to reduce allele frequency differences between populations; 2. It can enhance genetic diversity within a population
67
Q

This is when individuals choose mates regardless of genotype/phenotype

A

Random mating

68
Q

This type of mating occurs when individuals do not mate randomly

A

Assortative mating

69
Q

What are the two types of assortative mating?

A

Positive and negative assortative mating

70
Q

This type of assortative mating occurs when individuals are more likely to mate due to similar phenotypic characteristics

A

Positive assortative mating

71
Q

This type of assortative mating occurs when individuals with dissimilar phenotypes mate preferentially

A

Negative assortative mating

72
Q

This is mating between genetically related individuals

A

Inbreeding

73
Q

This is mating between genetically unrelated individuals

A

Outbreeding

74
Q

In the absence of other evolutionary forces, are allele frequencies affected by in- or outbreeding?

A

No

75
Q

This scientist developed methods to quantify the degree of inbreeding

A

Gustave Malecot

76
Q

This can be computed by analyzing the degree of relatedness within a pedigree

A

Inbreeding coefficient (F)

77
Q

This is the probability that two alleles for a given gene in a particular individual will be identical because both copies are due to descent from a common ancestor

A

Inbreeding coefficient (F)

78
Q

What are the two steps for determining the coefficient of inbreeding for an individual?

A
  1. Identify all common ancestors of the individual; 2. Determine the inbreeding paths (shortest path through the pedigree that includes both parents and the common ancestor)
79
Q

How is the length of each inbreeding path calculated?

A

By adding all individuals in the path except the individual of interest

80
Q

What is the formula for finding the inbreeding coefficient (F)?

A

𝐹 = ∑ (1/2)^𝑛 (1+𝐹_𝐴)

81
Q

What does n stand for in the formula for inbreeding coefficient?

A

Number of individuals in inbreeding path

82
Q

What does F_A stand for in the formula for inbreeding coefficient?

A

Breeding coefficient of common ancestor

83
Q

This is another term for inbreeding coefficient

A

Fixation coefficient

84
Q

This is the probability that an allele will be fixed in the homozygous condition

A

Fixation coefficient

85
Q

In natural populations, as population size decreases and mate choices become more limited, does the value of F tend to increase or decrease?

A

Increase

86
Q

This raises the proportion of homozygotes and decreases the proportion of heterozygotes

A

Inbreeding

87
Q

This is the lowering of overall fitness in natural populations by inbreeding

A

Inbreeding depression

88
Q

In this source of genetic variation, the independent segregation of different chromosomes may give rise to new combinations of alleles in offspring

A

Independent assortment

89
Q

In this source of genetic variation, recombination between homologous chromosomes can also produce new combinations of alleles that are located on the same chromosome

A

Crossing over

90
Q

In this source of genetic variation, members of different species may breed with each other to produce hybrid offspring

A

Interspecies cross

91
Q

This source of genetic variation occurs in prokaryotes and can be in the form of conjugation, transduction or transformation

A

Prokaryotic gene transfer

92
Q

In this source of genetic variation, point mutations can occur within a gene to create single-nucleotide polymorphisms (SNPs); genes can be altered by small deletions and additions

A

New alleles

93
Q

In this source of genetic variation, events, such as misaligned crossovers, can add additional copies of a gene into a genome and lead to the formation of gene families

A

Gene duplications

94
Q

This source of genetic variation involves deletions, duplications, inversions and translocations, as well as aneuploid, polyploid and alloploid offspring

A

Chromosome structure and number

95
Q

In this source of genetic variation, new genes can be created when exons of a preexisting gene are rearranged to make a gene that encodes a protein with a new combination of domains

A

Exon shuffling

96
Q

In this source of genetic variation, genes from one species can be introduced into a different strain of the same species or into another species and become incorporated into that species’ genome

A

Horizontal gene transfer

97
Q

In this source of genetic variation, short repetitive sequences are common in genomes due to the occurrence of transposable elements and tandem arrays; the numbers and lengths of repetitive sequences tend to show considerable variation in natural populations

A

Changes in repetitive sequences

98
Q

What are at least six out of ten sources of genetic variation?

A
  1. Independent assortment; 2. Crossing over; 3. Interspecies crosses; 4. Prokaryotic gene transfer; 5. New alleles; 6. Gene duplications; 7. Chromosome structure and number changes; 8. Exon shuffling; 9. Horizontal gene transfer; 10. Changes in repetitive sequences
99
Q

These involve changes in genetic sequences and chromosome structure or number

A

Mutations

100
Q

These increase mutation rate

A

Mutagens

101
Q

This Russian geneticist was the first to suggest that mutational variability provides the raw material for evolution and new alleles

A

Sergei Chetverikov

102
Q

Sergei Chetverikov was the first geneticist to suggest the following two ideas about genetic mutations

A
  1. Mutational variability provides the raw material for evolution (but does not constitute evolution itself); 2. Mutation can provide new alleles (but does not act as the major force dictating the final balance)
103
Q

A new mutation may have one of these three effects on an individual

A

Beneficial, neutral, deleterious

104
Q

Which of the three types of mutations (beneficial, neutral, deleterious) is least likely to occur?

A

Beneficial mutation

105
Q

This is the probability that a gene will be altered by a new mutation

A

Mutation rate

106
Q

How is the mutation rate expressed?

A

As the number of new mutations in a given gene per generation

107
Q

What is the common range for mutation rate?

A

10^-5 to 10^-6 per generation

108
Q

Many proteins have this type of structure

A

Modular structure

109
Q

Many proteins have two or more of these, with different functions

A

Discrete domains

110
Q

Each domain in a protein tends to be encoded by one or a series of these

A

Exons

111
Q

This occurs when an exon and flanking introns are inserted into a gene

A

Exon shuffling

112
Q

Exon shuffling may be promoted by these

A

Transposable elements

113
Q

Exon shuffling can also be caused by these

A

Nonhomologous double crossovers

114
Q

This is the incorporation of genetic material from another organism without being the offspring of that organism

A

Horizontal gene transfer

115
Q

Horizontal gene transfer may account for this percentage range of variation in the genetic composition of modern prokaryotic species

A

20-30%

116
Q

Can horizontal gene transfer occur from prokaryotes to eukaryotes and vice versa?

A

Yes

117
Q

These are short sequences repeated many times in a genome

A

Repetitive sequences

118
Q

Repetitive sequences can originate via these

A

Transposable elements

119
Q

Repetitive sequences can be these, 1 to 6 base pair repeats, over less than a couple hundred base pairs

A

Microsatellites

120
Q

Microsatellites are also known as these

A

Short tandem repeats (STR)

121
Q

These repeats are 6 to 80 base pairs covering 100 to 20,000 base pairs

A

Minisatellites

122
Q

Repetitive sequences can undergo mutation which changes this

A

Number of repeat units

123
Q

Are the mechanisms that change micro- and minisatellite repeat numbers well understood?

A

No

124
Q

Changes in repetitive sequences may involve these two processes

A

Replication errors (strand slippage) or recombination

125
Q

This analyzes DNA from individuals based on the occurrence of repetitive sequences at specific sites in their genome

A

DNA fingerprinting (DNA profiling)

Genetics (11 decks)

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