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Oxford Ecology and evolution > Population Genetics 1 > Flashcards

Population Genetics 1 Flashcards

1
Q

Main idea of fitness

A

Individuals show variation in phenotypic traits linked to survival and competitive ability

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2
Q

Main idea of natural selection

A

Individuals that are most likely to reproduce pass on the heritable traits to future generations

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3
Q

Adapative radiation

A

Diversification of a group of organisms into forms filling different niches

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4
Q

Main idea of speciation

A

Over time populations become divergently adapted to different environments ultimately resulting in speciation

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5
Q

Three parts of Darwin’s theory

A

Fitness
Natural selection
Speciation

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6
Q

What is the Hardy Weinberg principle?

A

Provides mathematical equation that can be used to calculate frequency of the alleles of a particular gene in a population

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7
Q

What does the hardy Weinberg equation assume?

A

The proportion of dominant and recessive alleles
of any gene in a population

remains the same

from one generation to the next

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8
Q

Hardy Weinberg equation

A

P^2 +2pq + q^2 = 1

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9
Q

p

A

Frequency of dominant allele

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10
Q

q

A

Frequency of recessive allele

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11
Q

What rule do we need to calculate probability of getting homozygotes? (AA/bb)

A

Multiplication rule

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12
Q

What is the multiplication rule

A

The probability of two independent events both occurring is

the production of the probability of each event occurring

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13
Q

What rule do we need to calculate the probability of getting heterozygotes (Ab/ aB)

A

The addition Rule

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14
Q

What is the addition rule

A

Probability of any one of a set of mutually exclusive events occurring = The sum of the probabilities of the individual events

Eg. Probability of rolling a 3 with 2 dice roles

1/6 (probability of rolling a 2)x1/6(probability of second role being a 1) + 1/6(probability do first role being a 1)x1/6(probability of second role being a 2) = 2/36

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15
Q

Probability of getting PP (green in the guys diagram)

A 
Sperm = has p and q alleles 
Egg = has p and q alleles

Probability of getting two p alleles (two independent events occurring would be the zygote getting a p allele from speed and a p allele from egg) = product or probability of each event occurring (p x p)

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16
Q

Where 2PQ is derived from

A

Q x P

P x Q

Combined probability = the sum of probabilities of individual events (selection of a p and q allele = one event)

= 2pq

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17
Q

What does HW assume about mating and populations?

A

Mating is random

Populations are infinite in size

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18
Q

What does HW assume about mating and populations?

A

Mating is random

Populations are infinite in size

19
Q

Genetic drift

A

Stochastic changes in allele frequency due to chance in small populations

20
Q

Example of genetic drift

A

2 yellow peas, four green

Creature munches all four green
So just yellow peas left

Two yellow pease by chance produce all yellow peas

21
Q

What does genetic drift do

A

Reduces genetic variation

22
Q

If an allele becomes highly frequent because of genetic drift is that evolution?

A

Yes

Evolution is about changes in phenotypes over time (genetic drift can drive that)

Key thing about NS in comparison is it drives adaptation

23
Q

Relationship between strength of genetic drift and population size

A

As population size increases, strength of genetic drift increases

24
Q

Fitness

A

Relative reproductive rate of individual with a given genotype

25
Q

Selection coefficient (s)

A

Change in fitness associated with the allele when its homozygous

26
Q

When is an allele beneficial

A

When s>0

27
Q

When is an allele deleterious

A

When s<0

28
Q

What is dominance (h)

A

Extent to which the effect of the allele on fitness is masked when it’s heterozygous

29
Q

When is an allele completely dominant

A

When h = 1

30
Q

When is an allele completely recessive

A

When h = 0

31
Q

What two things does change in allele frequency depend on

A
  1. Fitness of each genotype

2. Average fitness of population

32
Q

How to calculate average fitness

A

Frequency of each genotype x it’s fitness

33
Q

Define selective sweep

A

When an allele goes from a low frequency to a very high frequency in a population

(Sweeping out all other genetic variation at that locus in the population)

34
Q

What is there to note about time taken for selective sweeps

A

It varies depending if it’s recessive, dominant or codominant

35
Q

VEVOX

Why does dominance accelerate adaption?

A

Rare mutations are almost never homozygous

(Recessive alleles can only produce a benefit/effect if they are homozygous because otherwise they just get masked by dominant allele. But it’s just a thing that in random mating recessive alleles are rare in homozygous form)

36
Q

Stickleback

A

Freshwater stickleback = loss of body armour

Marine sticklebacks = body armour

Freshwater lakes colonised by marine sticklebacks.

Introduced transgenic stickleback with recessive allele, found over time recessive allele increased in population

37
Q

What is the marine stickleback thing an example of?

A

X

38
Q

Define migration rate

A

Probability an allele copy arrives on an Island by migration

39
Q

How does migration prevent divergence between populations

XX

A

If you allow migration then over time the allele frequency converges to average frequency

40
Q

What does migration do?

A

Prevents genetic divergence between populations

Strong homogenising force in population genetics

41
Q

Genetic diversity is shaped by interplay between

A

Migration = increases genetic diversity
Genetic drift = reduces diversity by chance
Selection = selective sweep (reduces diversity as high fitness allele sweeps low fitness allele out of population)

42
Q

Alcohol dehydrogenase in drosophila example

A

Frequency of F allele decreases at lower latitudes (looks like it’s selection)

Overall trend for F allele at top but lots of variation around that (this is being shaped by migration, selection and drift)

43
Q

Why does population genetics matter?

What two things does it help us understand and what does it fuel

A

Genetic diversity provides fuel for adaptation

  1. How genetic variation is organised
  2. How selection alter genetic diversity

Oxford Ecology and evolution (13 decks)

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