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BIO106 - Evolutionary Biology > Lesson 5: Evolutionary Mechanisms - Genetic Drift (and Inbreeding) > Flashcards

Lesson 5: Evolutionary Mechanisms - Genetic Drift (and Inbreeding) Flashcards

1
Q

what does deviation fro Hardy-Weinberg Equilibrium indicate

A

evolution is happening

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2
Q

Four major evolutionary mechanisms that alter allele frequencies in populations

A
  1. genetic drift
  2. natural selection
  3. mutation
  4. migration
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3
Q

One evolutionary mechanism that alters heritable expression of those alleles

A

epigenetic inheritance

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4
Q

what does natural selection act on

A

genetic / epigenetic variation

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5
Q

what does mutation generate

A

genetic variation

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6
Q

epigenetic modification changes what

A

expression of genes

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7
Q

what does genetic drift cause

A
  • fluctuations in allele frequencies
  • can reduce genetic variation
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8
Q
  • can act as a homogenizing force
  • if two populations are different, this can reduce differences
  • population could go out of HW equilibrium
A

migration

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9
Q

migration can act as a __ __

A

homogenizing force

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10
Q

primarily the natural occurring development or body of water that separates and detaches as area from others

A

geographic barrier

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11
Q

Two types of migration

A
  1. immigration
  2. emigration
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12
Q

could introuduce genetic variation into a population

A

immigration

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13
Q

could reduce genetic variation in a population

A

emigration

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14
Q
  • regarded inbreeding and genetic drift as particularly important genetic mechanisms
  • worked on agricultural stocks and was consequently
A

Sewall Wright

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15
Q

what did Sewall Wright regard as particularly important genetic mechanisms

A
  • Inbreeding
  • Genetic Drift
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16
Q

what could inbreeding and genetic drift generate according to Sewall Wright

A

new gene interactions

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17
Q

Null Model

A
  1. no evolution
  2. no selection
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18
Q

no evolution

A

population in HWE

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19
Q

no selection

A
  • no natural selection
  • include genetic drift
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20
Q

null model that tests for natural selection should include __

A

demography

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21
Q

directly affects the level of genetic drift acting on a population

A

population size

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22
Q

who focused more on importance of genetic drift during the evolutionary synthesis

A

Sewall Wright

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23
Q

who focused more on importance of natural selection during the evolutionary synthesis

A

Ronald Fisher

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24
Q

when did the emphasis of genetic drift resurge

A

1970s, 80s (w/ Kimura’s “neutral theory”

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25
Q

wrote “The Neutral Theory of Molecular Evolution”

A

Motoo Kimura

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26
Q

most evolutionary changes at the molecular level are caused by random genetic drift of selectively neutral nucleotide substitutions

A

neutral theory of molecular evolution by Kimura

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27
Q

molecular evolution takes place at a roughly __ __

A

constant rate

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28
Q
  • average rate at which a species’ genome accumulates mutations
  • used to measure their evolutionary divergence and in other calculations
A

molecular clock

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29
Q

changes in allele frequency from one generation to the next simply due to chance (sampling error)

A

random genetic drift

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30
Q

what kind of evolutionary force is genetic drift

A

non adaptative

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31
Q

Two types of evolutionary force

A
  1. Non adaptive
  2. Adaptative
32
Q

primarily random, including mutation, genetic drift, and recombination.

A

Non-adaptive forces

33
Q

what are the Non-adaptive forces

A
  1. mutation
  2. genetic drift
  3. recombination
34
Q

depend on the relative or absolute fitness of individuals within a population, such as natural selection

A

Adaptive forces

35
Q

What are the Adaptive forces

A

natural selection

36
Q

when does genetic drift happen

A
  • populations are limited in size
  • violating HW assumption of infinite population size
37
Q

when population is large, chance events … ?

A

cancel each other out

38
Q

when population is small, random differences in reproductive success begin to …?

A

matter much more

39
Q

in evolution, what is meant when we talk about population size

A

effective population size

40
Q

who introduced the concept of effective population size

A

Sewall Wright

41
Q

the number of individuals in a population that actually contribute offspring to the next generation

A

effective population size

42
Q

lead to an effective population size that is smaller than the census size

A
  1. unequal sex ratio
  2. variation in no. of offspring
  3. overlapping generations
  4. fluctuations in population size
  5. nonrandom mating
43
Q

Ne formula

A

= 4NmNf / (Nm+Nf)

44
Q

actual unit of evolution

A

Ne

45
Q

Element of chance in:

A
  1. who leaves offspring
  2. no. of offspring
  3. which offspring survive (which gametes, which alleles)
46
Q

Consequence of Genetic Drift
Population size is reduced:

A
  1. Allelic Level
  2. Genotypic Level
47
Q

Consequence of Genetic Drift
Population size is reduced:
- allelic level

A

random fixation of alleles (loss of alleles)

48
Q

Consequence of Genetic Drift
Population size is reduced:
- genotypic level

A

loss of heterozygosity (because of fewere alleles)

49
Q

extreme example of genetic drift that happens when the size of a population is severely reduced

A

bottleneck effect

50
Q
  • when an allele frequency becomes 100%
  • other alleles are lost by chance
A

fixation

51
Q

probability of fixation of an allele = ?

A

allele’s starting frequency

52
Q

as population get smaller, the probability of fixation goes __

A

goes up

53
Q

frequency of heterozygotes in a population

A

heterozygosity

54
Q

frequency of heterozygotes in the next generation

A

Hg+1

55
Q

Hg+1 formula

A

Hg+1 = Hg (1- 1/2N)

56
Q

loss of allelic variation due to genetic drift results in what

A

increased homozygosity

57
Q

no genetic variation = ?

A

no natural selection

58
Q

what happens to natural selection when there is genetic drift

A

less efficient

59
Q

where is natural selection more efficient

A

larger populations

60
Q

How to detect genetic drift

A
  1. random fluctuations in allele frequencies
  2. fluctuations in non-coding and non-functional regions of the genome
  3. same pattern of fluctuations across these regions of the genome
  4. fluctuations in allele frequencies correspond to demography of population (population size)
61
Q

genetic drift often leads to what

A

inbreeding

62
Q

mating among genetic relatives, often because of small population size

A

inbreeding

63
Q

measure of homozygosity

A

F = fixation index

64
Q

measure of relatedness between two individuals

A

inbreeding coefficient

65
Q

Consequences of inbreeding

A
  1. exposure of recessive alleles (may be deleterious)
  2. inbreeding depression
  3. lower genotypic diversity
66
Q

could be subjected to selection

A

exposure of recessive alleles

67
Q

reduction in survival and fitness

A

inbreeding depression

68
Q

poor response to natural selection

A

lower genotypic diversity

69
Q

on average, each of us carries __ lethal recessive alleles

A

3-5

70
Q

Examples of genetic diseases due to inbreeding

A
  1. porphyria
  2. acromegaly
  3. hemophilia
71
Q
  • accumulation of porphyrin precursors
  • causes insanity
  • dominant, but more intense in homozygous form
A

porphyria

72
Q
  • overproduction of GH by the pituitary gland
  • recessive
A

acromegaly

73
Q
  • victoria’s secret
  • x-linked, shows up n males more
A

hemophilia

74
Q

extreme consequence of genetic drift

A

inbreeding

75
Q

When is genetic drift LEAST likely to operate

A

when population is very very large

76
Q

selection acts __ in inbred populations to remove deleterious recessive alleles

A

faster

BIO106 - Evolutionary Biology (20 decks)

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