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Principals of Evolution > Population Genetics I: Natural Selection > Flashcards

Population Genetics I: Natural Selection Flashcards

1
Q

Hardy-Weinberg Equation

A

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

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2
Q

within a population, do allele frequencies change from generation to generation?

A

no, allele frequencies will not change

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3
Q

what happens if the random mating assumption is violated?

A

genotype frequencies will change but allele frequencies will not

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4
Q

evolutionary processes

A
  • infinite population size
  • no migration
  • no mutation
  • no natural selection
  • mating is random
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5
Q

how many rounds of random mating is required to reestablish HW equilibrium?

A

one round of random mating

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6
Q

how to find the frequency of the A allele

A

p^2 + (1/2) 2pq

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7
Q

how to calculate the expected number of individuals with a genotype given allele frequencies

A

p^2
2pq
q^2
then total the answers

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8
Q

steps to a statistical test

A
  • have a hypothesis
  • define the expectation under the null hypothesis of no effect
  • collect data
  • compute a test statistic
  • find the probability of your test statistic
  • interpret your results
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9
Q

chi squared test

A

X^2 = sum (observed - expected)^2 / expected

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10
Q

critical value of X^2 distribution

A

3.84

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11
Q

absolute fitness

A

the average lifetime reproductive success of individuals with that phenotype

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12
Q

fitness component

A

an individual score on a measure of performance expected to correlate strongly with the genetic contribution to the next generation

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13
Q

examples of fitness components

A
  • survival
  • fecundity
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14
Q

natural selection

A

a consequence of differences in fitness between individuals that differ in phenotype

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15
Q

symbol for relative fitness

A

W

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16
Q

relative fitness

A

the fitness of a phenotype compared with others in the population

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17
Q

what is the maximum relative fitness typically equal to

A

1

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18
Q

how to calculate relative fitness

A

absolute fitness / maximum absolute fitness

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19
Q

how to calculate the allele frequencies at time t0

A

p = AA / total t0 + 0.5 (Aa / total t0)
q = aa / total t0 + 0.5 (Aa / total t0)

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20
Q

how to calculate the expected # of individuals at time t1

A

AA = p^2 + total t1
Aa = 2pq + total t1
aa = q + total t1
add all together

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21
Q

how to calculate absolute fitness

A

observed at time t1 / # expected at time t1
- done for all genotypes

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22
Q

how to calculate relative fitness

A

all fitnesses / maximum absolute fitness

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23
Q

how to see there was evolution?

A

delta q = q1 - q0

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24
Q

fitness is a _________, not an _________

A

description, explanation

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25
Q

how did Herbert Spenser define natural selection?

A
  • he defined natural selection as survival of the fittest
  • this is not an accurate definition
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26
Q

how does an advantageous trait contribute to an organisms?

A

the organisms survival and reproductive success

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27
Q

what does the phenotype of an organism in relation to the environment it inhabits determine?

A

how fit that organism is

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28
Q

fitness is…

A

context dependent

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29
Q

the general selection model equation

A

delta q = pq [q (W3 - W2) + P (W2 - W1)] / W

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30
Q

how to calculate average effect of an allele substitution

A

[q (W3 - W2) + p (W2 - W1)]

31
Q

what does the general selection model quanify?

A

the relationship between allele frequencies and fitness

32
Q

the greater the difference between the relative fitnesses…

A

the greater the rate of evolution

33
Q

S

A

selection coefficient

34
Q

AA

A

W1 = 1

35
Q

Aa

A

W2 = 1a

36
Q

aa

A

W3 = 1 - S

37
Q

how to calculate selection with dominance

A

delta q = -spq^2 / 1 - sq^2

38
Q

directional selection

A

a mode of natural selection in which a phenotype is consistently favored, causing allele frequencies to shift over time in the direction of that phenotype

39
Q

the rate of change in allele frequencies

A

a function of the allele frequencies, the relative fitness values, and the mean population fitness in the population

40
Q

does the directional selection always increase mean population fitness?

A

yes

41
Q

how to calculate the selection with dominance when the fitness of the homozygous recessive = 0

A

qn = q0 / 1 + nq0

42
Q

eugenics

A

the study and practice of control over the evolution of human populations in an effort to decrease the frequency of undesirable traits

43
Q

cystic fibrosis

A

cell surface protein expressed in the mucus lining of the intestines and lungs

44
Q

what does CTFR enable?

A

cells to ingest and destroy the bacterium

45
Q

how does cystic fibrosis form?

A

homozygotes for loss-of-function mutations suffer chronic infections with the bacterium

46
Q

how to calculate heterozygote advantage

A

p = S2 / S1 + S2
q = S1 / S1 + S2

47
Q

balancing selection

A

forms of natural selection that maintain variation within a population

48
Q

Hb^A

A

normal allele in hemoglobin

49
Q

Hb^S

A

sickle cell allele in hemoglobin

50
Q

what are homozygotes for the Hb^A allele susceptible to?

A

malaria in West Africa

51
Q

what is malaria caused by?

A

protozoan Alveolata

52
Q

symptoms and effects of malaria and sickle cell anemia

A
  • invades red blood cells & eats the hemoglobin
  • malaria causes severe fevers
  • infected blood cells clump up and cause dangerous clots
53
Q

Hb^S allele anemia

A
  • the red blood cells do not carry oxygen well and form a sickle shape when they do not have oxygen
  • the blocks blood vessels and eventually leads to death
  • when sickle cells pass through the spleen they are detected by white blood cells as defective and destroyed
54
Q

Hb^A Hb^S heterozygotes

A

resistant to malaria but suffer mild anemia

55
Q

is S positive or negative in underdominance?

A

negative

56
Q

mutation

A
  • fundamental to evolutionary theory
  • the raw material of the evolutionary process
57
Q

mutation includes

A
  • point mutations
  • indels
  • gene duplication
  • transposable elements
  • chromosomal mutations
  • genome level mutations
58
Q

is mutation planned or random?

A

mutation has causes, but is random with respect to adaptive needs

59
Q

the environment doe snot induce adaptive mutations

A

no “inheritance of acquired characters”

60
Q

what prevents mutations?

A

developmental constraints prevent many mutations from ever being expressed at the phenotypic level

61
Q

purifying selection

A

selection against deleterious mutation

62
Q

how is purifying selection removed?

A

removed by selection if dominant or codominant

63
Q

u = A –> a

A

forward mutation rate

64
Q

v = a –> A

A

backward mutation rate

65
Q

how does mutation change the frequency of allele a?

A

if deltaqm is the per generation change in q, due to mutation, then
detlaqm = pu -qv

66
Q

mutation without selection will…

A

increase the frequency of the a allele

67
Q

what happens when there is a selection against the aa genotype?

A

the frequency of the a allele declines

68
Q

selection without mutation will…

A

decrease the frequency of the a allele

69
Q

what happens at mutation selection balance?

A

a allele will achieve an equilibrium

70
Q

what kind of disease is spinal muscular atropy?

A

neurodegenerative disease

71
Q

neurodegenerative disease

A

degeneration of the muscles that control voluntary movement

72
Q

what causes neurodegenerative disease?

A

deletions at one locus

73
Q

what maintains neurodegenerative disease?

A

mutation/selection balance

Principals of Evolution (18 decks)

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