Allele frequency and types of selection

Question 1

allele frequency

Answer 1

• when 2 alleles in a population = represented by p&q
• all frequencies must add up to 1
• p + q = 1

Question 2

Hardy-Weinberg principle

Answer 2

predicts:
- under certain conditions, allele genotype frequencies will remain constant
- related in a specific way
- population needs to be at equilibrium/not evolving

Question 3

frequency of AA genotype =

Answer 3

p squared

Question 4

frequency of aa genotype =

Answer 4

q squared

Question 5

frequency of Aa genotype =

Answer 5

2pq

Question 6

p squared + 2pq + q squared =

Answer 6

1

Question 7

Hardy-Weinberg equilibrium necessities

Answer 7

• all individuals have equal probabilities of surviving & reproducing
  = violated by selection
• population is infinitely large
  = violated by genetic drift
• genes not added to or removed from population by migration
  = violated by gene flow
• DNA sequencing does not change
  = violated if there’s a mutation
• mating is random
  = violated by inbreeding and/or sexual selection

Question 8

three conditions of selection

Answer 8

• variation is a trait
• heritability is a trait
• differential fitness conferred by a trait

Question 9

qualitative traits

Answer 9

• have discrete qualities
• controlled by alleles at a single locus

Question 10

quantitative traits

Answer 10

• show continuous variation
• influenced by genes at many loci as well as by environment

Question 11

directional selection

Answer 11

• favours one extreme value/trait
• a.k.a positive selection
• individuals at one extreme have most fitness = trend towards extreme

Question 12

stabilising selection

Answer 12

• favours average values
• a.k.a balancing selection
• individuals closes to mean have highest fitness

Question 13

disruptive selection

Answer 13

• favours both extreme values
• a.k.a diversifying selection
• individuals at both extremes have high fitness

Question 14

sexual selection can operate

Answer 14

• intra-sexually
• inter-sexually
• pre-copulatory
• post-copulatory

Question 15

intra-sexually

Answer 15

• competitions between members of same sax

Question 16

inter-sexually

Answer 16

• mate choice

Question 17

pre-copulatory

Answer 17

• acquiring mating opportunities

Question 18

post-copulatory

Answer 18

• events that occur during and after mating

Question 19

direct benefits of sexually selective traits

Answer 19

some cases, honest signals of parental quality
- bright male house finches are better providers

Question 20

indirect benefits of sexually selective traits

Answer 20

sexy sons (runaway selection)
- females express preference for male treat
- no benefit to her
- sons express trait females preferred, increasing sons reproductive success

good genes
- genes enable males to develop impressive ornaments or fighting ability
-may indicate overall genetic quality
- song repertoire size is associated w/ immunocompetence