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Bio113: Evolution > Selection, Gene Flow and Mutation > Flashcards

Selection, Gene Flow and Mutation Flashcards

1
Q

What level does selection occur at?

A

the phenotypic level

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2
Q

If an allele is dominant what would the fitness be of the heterozygote?

A

it would be the same as the dominant homozygote

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3
Q

If an allele is recessive what would the fitness be of the heterozygote?

A

it would be the same as the recessive homozygote

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4
Q

Name the types of selection (5)

A
  1. Directional
  2. Disruptive
  3. Stabilising
  4. Balancing
  5. Fluctuating
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5
Q

Describe directional selection

A

one allele is favoured over the other

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6
Q

Describe disruptive selection

A

extremes of a trait are favoured

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7
Q

Describe stabilising selection

A

variation is reduced

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8
Q

Describe balancing selection

A

large amounts of alleles are present in a population

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9
Q

Describe fluctuating selection

A

the direction of selection changes overtime

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10
Q

What type of selection is being shown in this graph?

A

balancing selection

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11
Q

What type of selection is being shown in this graph?

A

disruptive selection

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12
Q

What type of selection is being shown in this graph?

A

directional selection

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13
Q

What type of selection is being shown in this graph?

A

stabilising selection

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14
Q

What does the line of best fit represent in an evolutionary graph?

A

selection

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15
Q

What is always happening in the background?

A

drift

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16
Q

Why can it hard to eradicate a recessive trait?

A
  • heterozygote fitness is equal to homozygous dominant
  • there will be no fixation
  • recessive allele can hide in the heterozygote
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17
Q

Give an example of a recessive disease

A

Ellis-van Creveld syndrome

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18
Q

Why is it easier to eradicate a dominant disease?

A
  • heterozygote fitness is equal to homozygous dominant
  • there will be fixation
  • recessive allele cannot hide in the heterozygote
  • the only genotype selected for will be the recessive homozygote
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19
Q

Give an example of a dominant disease

A

Marfan syndrome

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20
Q

What is overdominance?

A

the heterozygote has the greatest fitness and is therefore preferred

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21
Q

What is underdominance?

A

the heterozygote has the lowest fitness and is therefore not preferred

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22
Q

What will the allele frequency be under overdominace/heterozygote advantage?

A

at equilibrium because in a heterozygote there are two alleles so if you had a high allele frequency of one allele then it is more likely it would be present in homozygotes which is not preferred

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23
Q

When would there be fixation in overdominance/ heterozygote advantage?

A

if the original allele frequency was at fiaxtion, so there is only homozygotes present

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24
Q

How would you change the point of equilibrium in overdominance/ heterozygote advantage?

A

by changing the fitness levels of the homozygotes

25
Q

What would the allele frequencies be like in underdominance/ heterozygote disadvantage?

A

common (fit) alleles are driven to fixation

rare (unfit) alleles are driven out of the population

this is because if there are two alleles then they can exist as heterozygotes which is selected against

26
Q

Can you reach equilibrium in underdominance /heterozygote disadvantage?

A

yes but it is very unstable

27
Q

What would happen if new mutations arised in underdominance/ heterozygote disadvantage?

A

they would almost immediately be wiped out

28
Q

What is frequency dependent selection?

A

a type of selection where rare alleles are favoured

29
Q

Describe frequency dependent selection

A

rare allele is favoured until it is not rare anymore due to an increase in the allele frequency of those alleles, after this the other allele, which is now rare, will be favoured

30
Q

Give an example of frequency dependent selection

A

batesian mimicry

31
Q

Describe batesian mimicry

A

when an edible organism mimics a poisonous one

32
Q

Explain why batesian mimicry is an example of frequency dependent selection

A
  • predators will believe mimic is poisonous so won’t eat it
  • the mimic is selected for
  • mimic populations will increase
  • eventually there will be too many mimics so predators will try eating them
  • the mimic is no longer selected for
  • the non-mimic population will increase
  • the cycle will repeat
33
Q

What is meant by gene flow?

A

the process by which alleles are moved from one population to another

34
Q

True or False

The movement of individuals always means the movement in genes

Give an explanation why

A

False

because the moving individual may not be able to breed with the other populations so the genes will not be transfered to offspring

35
Q

True or False

Gene flow can only be one-dimensional

Give a reason why

A

False

it can be both multi-dimensional and one-dimensional

36
Q

What will happen if there is no gene flow?

A

populations will become genetically differentiated from each other

37
Q

What does it mean if populations homogenise?

A

individuals within the population become very similar, almost like they are 1

38
Q

What can gene flow cause?

A

lost genetic variation in a population

39
Q

What do mutations cause?

A

the production of genetic variation

40
Q

What do most cases of mutation cause?

A

no effect or very slight change

41
Q

True of False

Mutations can improve an organisms chance of survival

Explain your answer

A

True

some mutations can improve an organisms fitness so it will will have an increased chance of survival

42
Q

Name the small scale mutations that can occur (4)

A
  • point mutation
  • insertion
  • deletion
  • frame shift
43
Q

Explain what frame shift is

A

a change in the amino acid sequence

this applies to insertion and deletion events

44
Q

Explain what point mutation is

A

one base is swapped for another

45
Q

Give an example of a disease that is caused by the following small scale mutation:

point mutation

A

sickle cell anaemia

46
Q

Give an example of a disease that is caused by the following small scale mutation:

insertion

A

huntingtons disease

47
Q

Give an example of a disease that is caused by the following small scale mutation:

deletion

A

Duchenne muscular dystrophy

48
Q

Give an example of a disease that is caused by the following small scale mutation:

frame shift

A

Chrohn’s disease

this is currently being debated

49
Q

Name the large scale mutations that can occur (6)

A
  • ​large scale insertion
  • large scale deletion
  • inversion
  • duplication
  • insertion from another chromosome
  • translocation
50
Q

Describe what is meant by translocation

A

swapping of sections of chromosomes between chromosomes

51
Q

What is polysomy?

A

there is an extra copy of a chromosome

52
Q

Give an example of a disease caused by polysomy and name the chromosome it effects

A

Down’s Syndrome

there is an extra copy of the chromosome 21

53
Q

What type of very large scale duplication is used in the agricultural industry?

A

whole genome duplication

54
Q

Why can whole genome duplication be a good thing?

A

it yields larger fruits/crops

55
Q

Give an example of whole genome duplication

A

wheat

56
Q

What is the downside to using whole genome duplication in crops?

A

there is a large amount of ‘spare’ DNA which is more likely to mutate

57
Q

What is the effect of changing population sizes on the rate of mutation?

A

no change

the rate of mutation is independent of the size of a population

58
Q

What can mutation cause?

A

the re-introduction of lost genetic information

59
Q

What does mutation induce?

A

genetic variation

Bio113: Evolution (3 decks)

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