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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

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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
wrote "The Neutral Theory of Molecular Evolution"
Motoo Kimura
26
most evolutionary changes at the molecular level are caused by random genetic drift of selectively neutral nucleotide substitutions
neutral theory of molecular evolution by Kimura
27
molecular evolution takes place at a roughly __ __
constant rate
28
- average rate at which a species' genome accumulates mutations - used to measure their evolutionary divergence and in other calculations
molecular clock
29
changes in allele frequency from one generation to the next simply due to chance (sampling error)
random genetic drift
30
what kind of evolutionary force is genetic drift
non adaptative
31
Two types of evolutionary force
1. Non adaptive 2. Adaptative
32
primarily random, including mutation, genetic drift, and recombination.
Non-adaptive forces
33
what are the Non-adaptive forces
1. mutation 2. genetic drift 3. recombination
34
depend on the relative or absolute fitness of individuals within a population, such as natural selection
Adaptive forces
35
What are the Adaptive forces
natural selection
36
when does genetic drift happen
- populations are limited in size - violating HW assumption of infinite population size
37
when population is large, chance events ... ?
cancel each other out
38
when population is small, random differences in reproductive success begin to ...?
matter much more
39
in evolution, what is meant when we talk about population size
effective population size
40
who introduced the concept of effective population size
Sewall Wright
41
the number of individuals in a population that actually contribute offspring to the next generation
effective population size
42
lead to an effective population size that is smaller than the census size
1. unequal sex ratio 2. variation in no. of offspring 3. overlapping generations 4. fluctuations in population size 5. nonrandom mating
43
Ne formula
= 4NmNf / (Nm+Nf)
44
actual unit of evolution
Ne
45
Element of chance in:
1. who leaves offspring 2. no. of offspring 3. which offspring survive (which gametes, which alleles)
46
Consequence of Genetic Drift Population size is reduced:
1. Allelic Level 2. Genotypic Level
47
Consequence of Genetic Drift Population size is reduced: - allelic level
random fixation of alleles (loss of alleles)
48
Consequence of Genetic Drift Population size is reduced: - genotypic level
loss of heterozygosity (because of fewere alleles)
49
extreme example of genetic drift that happens when the size of a population is severely reduced
bottleneck effect
50
- when an allele frequency becomes 100% - other alleles are lost by chance
fixation
51
probability of fixation of an allele = ?
allele's starting frequency
52
as population get smaller, the probability of fixation goes __
goes up
53
frequency of heterozygotes in a population
heterozygosity
54
frequency of heterozygotes in the next generation
Hg+1
55
Hg+1 formula
Hg+1 = Hg (1- 1/2N)
56
loss of allelic variation due to genetic drift results in what
increased homozygosity
57
no genetic variation = ?
no natural selection
58
what happens to natural selection when there is genetic drift
less efficient
59
where is natural selection more efficient
larger populations
60
How to detect genetic drift
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
genetic drift often leads to what
inbreeding
62
mating among genetic relatives, often because of small population size
inbreeding
63
measure of homozygosity
F = fixation index
64
measure of relatedness between two individuals
inbreeding coefficient
65
Consequences of inbreeding
1. exposure of recessive alleles (may be deleterious) 2. inbreeding depression 3. lower genotypic diversity
66
could be subjected to selection
exposure of recessive alleles
67
reduction in survival and fitness
inbreeding depression
68
poor response to natural selection
lower genotypic diversity
69
on average, each of us carries __ lethal recessive alleles
3-5
70
Examples of genetic diseases due to inbreeding
1. porphyria 2. acromegaly 3. hemophilia
71
- accumulation of porphyrin precursors - causes insanity - dominant, but more intense in homozygous form
porphyria
72
- overproduction of GH by the pituitary gland - recessive
acromegaly
73
- victoria's secret - x-linked, shows up n males more
hemophilia
74
extreme consequence of genetic drift
inbreeding
75
When is genetic drift LEAST likely to operate
when population is very very large
76
selection acts __ in inbred populations to remove deleterious recessive alleles
faster

BIO106 - Evolutionary Biology (20 decks)

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