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Evolution > In class notes > Flashcards

In class notes Flashcards

1
Q

How many base pairs are in the human genome?

A

6 billion pairs

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2
Q

What is a synonymous substitution?

A

nucleotide substitution that don’t cause an amino acid change

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3
Q

What is a non-synonymous substitution?

A

nucleotide change that causes an amino acid change

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4
Q

What is the rate of synonymous to non-synonymous substitutions indicate

A

used as an indicator of selection pressure

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5
Q

What is a gene

A

stretch of dna/rna that is subject to natural selection

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6
Q

what is an allele

A

a variant of a gene

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7
Q

what is a locus

A

place where you find a gene in a genome

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8
Q

What is a genotype

A

diploid contingent of alleles

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9
Q

what is my haplotype

A

haploid contingent of alleles

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10
Q

what is a phenotype

A
  • expression of genotype
  • what your genotype codes for
  • things that selection can act on
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11
Q

what is a snp

A
  • single nucleotide polymorphism

- a variation at a single position in a dna sequence among individuals

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12
Q

Do SNPs occur normally throughout an individuals DNA

A
  • yes, most have no effect on health or development

- when they take place in a gene or near it in the regulatory region they can have negative effects on gene

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13
Q

What is biological evolution

A

changes in gene frequency over generations

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14
Q

what does biological evolution lead to

A

descent with modification

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15
Q

what is descent with modification

A

the idea that species change over time, give rise to new species, and share a common ancestor

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16
Q

What does descent with modification lead to

A

production of new genes and new traits and splitting of lineages into new species

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17
Q

is evolution change within individuals?

A

no

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18
Q

What is phenotypic plasticity

A
  • changes in an organisms behaviour, morphology, and physiology in response to a unique environment
  • ability of a genotype to express different phenotypes depending on the environment
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19
Q

what are the causes of evolution?

A

selection
mutation
migration
drift

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20
Q

What is selection

A

the only known cause of design

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21
Q

What is mutation

A

“fuel” of evolution

random

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22
Q

What is migration

A

quick way to get “fuel” (mutations)

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23
Q

what is drift

A

powerful retarding force, random

  • change in allele frequency within a population over time
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24
Q

is evolution synonymous with natural selection

A

no

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25
Q

what is evolutionary fitness (Darwinian fitness)

A

an individuals relative contribution of alleles to the next generation

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26
Q

What is evolutionary fitness a function of

A

p (survival)

E (number of offspring)

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27
Q

What is adaptation

A

a trait that causes an increase in fitness relative to other real or imagined traits via its relatively good fit to a particular environment

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28
Q

what are Darwins 4 postulates for evolution by natural selection

A
  • individuals vary in phenotype
  • some phenotypic variation is passed on to offspring
  • more offspring are produced that can survive or reproduce
  • survival and reproduction is not random, but is related tp aspects of phenotypic variation
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29
Q

Are humans particularly variable

A

not particularly for size

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30
Q

what is heritability

A

degree to which individuals are similar because they have the same genotype

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31
Q

What is a good way to measure heritability

A

cross-fostering or twin experiments

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32
Q

what must occur if there is a differential transmission of genetic material mediated by the environment

A

evolution by natural selection

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33
Q

What is differential fitness

A

that survival and reproduction vary between individuals

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34
Q

Why is HIV fatal to humans

A
  • evolution by natural selection has no foresight
  • transmission allows HIV to persist even though host dies
  • there hasn’t been enough time for humans to evolve resistance
  • there hasn’t been enough time for co-evolution to occur between humans and HIV
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35
Q

When will there be no natural selection on a trait

A

if there is no variation, if variation isn’t heritable, and if variation is heritable but it doesn’t differentially affect survival or reproduction

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36
Q

do individuals evolve

A

no

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37
Q

does selection act for the good of the lineage

A

no

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38
Q

does natural selection look ahead

A

no

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39
Q

does natural selection create variation

A

no, it actually erodes variation by selecting against trait s

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40
Q

what creates variation

A

mutations

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41
Q

what causes gene frequencies to change

A

mutation

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42
Q

what are the types of variation

A

genetic, environmental

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43
Q

what is genetic variation

A

variation due to different alleles at a locus
fuel needed
fuel needed to power evolution by natural selection powered by mutations

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44
Q

what is environmental variation

A

variation due to environments

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45
Q

is environmental variation

A

heritable

46
Q

What is genotype by environment variation

A

variation due to interactions between genes and the environment
can also be fuel for selection since phenotypic plasticity can be adaptive

47
Q

what is a mutation

A

any change in the nucleotide sequence

48
Q

how do you know if a mutation is heritable

A

check if its a germ line mutation

49
Q

what is a germ line mutation

A

mutation occurs in an egg or sperm cell

50
Q

what happens if a mutant cell is incorporated in a zygote

A

all cells of the progeny will contain the mutation

51
Q

what is a somatic mutation

A

mutation that occurs in a body cell other than egg/sperm

occurs in one cell and then is passed on via cell division

52
Q

what are the types of mutations

A 
point mutation
insertion
deletion
duplication 
inversion
chromosome fusion 
aneuploidy/ polyploidy
53
Q

What is a point mutation

A

a single base pair change from one nucleotide to another

54
Q

what causes point mutations

A

external factors that damage DNA followed by polymerase repairing it “incorrectly”

errors during DNA replication by polymerase enzymes

and then these mutations must evade corrections to become persistent mutations

55
Q

what type of mutation is Huntington’s disease an example of

A

insertion

56
Q

what type of mutation is cystic fibrosis an example of

A

deletion

57
Q

what is a gene duplication

A

a segment of dna is copied more than once

58
Q

what causes gene duplications

A

usually caused by an unequal crossing over or retroposition

59
Q

what is retroposition

A

a mechanism that creates duplicate gene copies in new genomic positions through reverse transcription of mRNAs from source genes

60
Q

what leads to copy number variation

A

duplication

61
Q

what is copy number variation

A

phenomenon in which sections of the genome are repeated and the number of repeats vary among individuals

62
Q

what are copy number variations associated with

A

disease in humans and rapid evolution

63
Q

what is an inversion

A

a region of DNA that has been flipped so genes are in reverse order

64
Q

What cause inversions

A

faulty repair

65
Q

what happens when one chromosome copy contains inversions and the other doesn’t

A

they cannot align properly during meiosis, resulting in very little crossing over. When crossing over does occur offspring typically cannot reproduce since they are missing genes

66
Q

why do inversions tend to be inherited as a unit

A

since inversions lead to lower levels of crossing over, causing tighter linkage among loci within the inversion

67
Q

what is human chromosome 2 a result of

A

end-to-end fusion of two ancestral chromosomes

68
Q

what is aneuploidy

A

when chromosomes are lost leading to an abnormal number of chromosomes

69
Q

what is polyploidy

A

when chromosomes are duplicated leading to an abnormal number of chromosomes

70
Q

what is a - s mean

A

means it is selected against

71
Q

what is a + s

A

means it is selected for

72
Q

when do most mutations occur

A

during cell division

73
Q

where do 2/3 of new mutations in humans come from

A

males since sperm is associated with more cell divisions than eggs

74
Q

what organs are most likely to get cancer

A

organs with more cell divisions carry more somatic mutations

75
Q

what is the average germ line mutation rate

A

1.0x10^-8

76
Q

how many basepairs is a haploid human genome

A

3.2x10^9 base pairs

77
Q

is genetic drift the result of selection

A

no

78
Q

is genetic drift adaptive

A

no

79
Q

what is genetic drift

A

random process that results in a change of allele frequency

a random sampling error that in the production of zygotes from a gene pool

80
Q

what is a sampling error

A

random discrepancy between theoretical and actual results

81
Q

what are the causes of drift

A

continuous (background) drift
Founder effect
population bottleneck

82
Q

what is continuous drift

A

just like from one generation to the next, some people have offspring and some dont, some alleles get passed

83
Q

what is a founder effect

A

when a small group of individuals become geographically isolated from the remainder of the population

or a small group of individuals colonize a new site

84
Q

what is a population bottleneck

A

a major reduction in population size which normally reduces genetic variation because at least some alleles are lost (especially rare ones)

85
Q

are age effects of drift greater in bigger or smaller populations

A

smaller

86
Q

What is fixation

A

when one allele goes tp 100% frequency

change in gene pool from a state with multiple alleles to a state with only one

87
Q

does fixation occur faster is smaller or bigger populations

A

smaller

88
Q

what is heterozygosity

A

the possession of two different alleles of a particular genes

89
Q

What happens to heterozygosity as alleles drift

A

it increases

90
Q

what is effective population size affected by

A

number of adults
sex ratio of breeders
fluctuations over time

91
Q

what are things that depress effective population size (Ne)

make the population genetically smaller than how it looks

A

variation in population size, variation in sex ratio, variations in family size

92
Q

what is inbreeding

A

mating with relatives

93
Q

what causes inbreeding

A

breeding systems
small populations
mating systems

94
Q

what ate the types of non-random mating

A

assortative mating

disassortative mating

95
Q

what is assortative mating

A

individuals choose mates that are phenotypically more similar than is expected by chance

96
Q

what is disassortative mating

A

individuals choose mates that are phenotypically less similar than is expected by chance

97
Q

what are the effects of inbreeding

A
  • increased homozygosity (which exposes recessive alleles to selection)
  • greater proportion of offspring will have lower fitness than offspring from outcrossing
98
Q

what is inbreeding depression

A

depressed fitness due to deleterious recessive alleles

99
Q

What can inbreeding accelerate

A

fixation

100
Q

why does drift counteract selection

A

because it is random

101
Q

why does inbreeding have different effects on different scales

A
  • potentially lowers fitness of the lineage that inbreeds and so is selected against
  • causes purging of bad alleles so it can increase fitness at a population level
102
Q

what is migration

A

movement of alleles between populations

103
Q

what causes migration

A

movement of individuals or gametes followed by mating or fertilization

104
Q

what is the effect of migration

A

immediate change in allele frequency in the recipient population
equilibrium is reached rapidly
island population ends up with the migrant allele frequency
usually one migrant/generation is enough to homogenize populations
-in absence of selection (or if alleles are selectively neutral) migration homogenize allele frequencies among populations

105
Q

what does p stand for

A

frequency of most common allele (usually the dominant one)

106
Q

what does q stand for

A

frequency of less common/ all other alleles

107
Q

what happens if selection and migration tend to increase frequencies of the same alleles

A

selection can amplify the effects of migration

108
Q

what happens if selection and migration are opposed

A

if selection > migration : then the differences between populations will be maintained even in the face of migration
if migration > selection: differences among populations will be reduced

109
Q

why is migration important for small populations

A

since migrant alleles may decrease fitness in the “island” population and thereby slow adaptive evolution. this could be a possible reason for the range limits of species

110
Q

how can migration speed up evolution

A

can bring in new alleles

111
Q

what does s stand for

A

selection coefficient

Evolution (8 decks)

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