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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

25
Q

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

A

Large populations

26
Q

What is the formula for the Hardy-Weinberg equation?

A

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

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

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

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

30
Q

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

A

Microevolution

31
Q

What is the source of new genetic variation in populations?

A

Mutation

32
Q

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

A

Natural selection, genetic drift, migration, nonrandom mating

33
Q

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

A

Charles Darwin and Alfred Russel Wallace

34
Q

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

A

Their reproductive success

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

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)

37
Q

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

A

1

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
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
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

41
Q

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

A

Balancing selection

42
Q

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

A

Disruptive (or diversifying selection)

43
Q

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

A

Stabilizing selection

44
Q

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

A

No

45
Q

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

A

Heterozygote

46
Q

This measures the degree to which a genotype is selected against

A

Selection coefficient

47
Q

What is the formula for selection coefficient?

A

s = 1 - w

48
Q

Heterozygote advantage can sometimes explain the high frequency of these alleles

A

Deleterious alleles

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

50
Q

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

A

Multiple genes

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

Genetics (9 decks)

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