Population Genetics 1

Question 1

Main idea of fitness

Answer 1

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

Question 2

Main idea of natural selection

Answer 2

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

Question 3

Adapative radiation

Answer 3

Diversification of a group of organisms into forms filling different niches

Question 4

Main idea of speciation

Answer 4

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

Question 5

Three parts of Darwin’s theory

Answer 5

Fitness
Natural selection
Speciation

Question 6

What is the Hardy Weinberg principle?

Answer 6

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

Question 7

What does the hardy Weinberg equation assume?

Answer 7

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

remains the same

from one generation to the next

Question 8

Hardy Weinberg equation

Answer 8

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

Question 9

p

Answer 9

Frequency of dominant allele

Question 10

q

Answer 10

Frequency of recessive allele

Question 11

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

Answer 11

Multiplication rule

Question 12

What is the multiplication rule

Answer 12

The probability of two independent events both occurring is

the production of the probability of each event occurring

Question 13

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

Answer 13

The addition Rule

Question 14

What is the addition rule

Answer 14

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

Question 15

Probability of getting PP (green in the guys diagram)

Answer 15

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)

Question 16

Where 2PQ is derived from

Answer 16

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

Question 17

What does HW assume about mating and populations?

Answer 17

Mating is random

Populations are infinite in size

Question 18

What does HW assume about mating and populations?

Answer 18

Mating is random

Populations are infinite in size

Question 19

Genetic drift

Answer 19

Stochastic changes in allele frequency due to chance in small populations

Question 20

Example of genetic drift

Answer 20

2 yellow peas, four green

Creature munches all four green
So just yellow peas left

Two yellow pease by chance produce all yellow peas

Question 21

What does genetic drift do

Answer 21

Reduces genetic variation

Question 22

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

Answer 22

Yes

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

Key thing about NS in comparison is it drives adaptation

Question 23

Relationship between strength of genetic drift and population size

Answer 23

As population size increases, strength of genetic drift increases

Question 24

Fitness

Answer 24

Relative reproductive rate of individual with a given genotype

Question 25

Selection coefficient (s)

Answer 25

Change in fitness associated with the allele when its homozygous

Question 26

When is an allele beneficial

Answer 26

When s>0

Question 27

When is an allele deleterious

Answer 27

When s<0

Question 28

What is dominance (h)

Answer 28

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

Question 29

When is an allele completely dominant

Answer 29

When h = 1

Question 30

When is an allele completely recessive

Answer 30

When h = 0

Question 31

What two things does change in allele frequency depend on

Answer 31

1. Fitness of each genotype | 2. Average fitness of population

Question 32

How to calculate average fitness

Answer 32

Frequency of each genotype x it’s fitness

Question 33

Define selective sweep

Answer 33

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)

Question 34

What is there to note about time taken for selective sweeps

Answer 34

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

Question 35

VEVOX | Why does dominance accelerate adaption?

Answer 35

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)

Question 36

Stickleback

Answer 36

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

Question 37

What is the marine stickleback thing an example of?

Answer 37

X

Question 38

Define migration rate

Answer 38

Probability an allele copy arrives on an Island by migration

Question 39

How does migration prevent divergence between populations | XX

Answer 39

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

Question 40

What does migration do?

Answer 40

Prevents genetic divergence between populations | Strong homogenising force in population genetics

Question 41

Genetic diversity is shaped by interplay between

Answer 41

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)

Question 42

Alcohol dehydrogenase in drosophila example

Answer 42

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)

Question 43

Why does population genetics matter? | What two things does it help us understand and what does it fuel

Answer 43

Genetic diversity provides fuel for adaptation 1. How genetic variation is organised 2. How selection alter genetic diversity