week 8 (population genetics)

Question 1

explain: HW equil.

Answer 1

• random mating and absence of evol. change leads to stable allele freq. in pop.
• calculates expected geno and allele freq. when no evolution

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

Question 2

name: assumptions of HW (6)

Answer 2

• pop size is infinite
• random mating
• no nat. sel.
• no migration/gene flow
• no mutations
• no genetic drift

Question 3

name: predictions of HW (4)

Answer 3

• allele freq. = stable over time
• allele distribution into genotypes is predictable
• stable equil. freq. of alleles and geno are maintained
• evol. and non-random mating effects are predictable

Question 4

explain: relative fitness (w) and selection coefficient

Answer 4

• quantifies nat. sel.
• w = 1 means highest reproductive success for a certain trait
• indiv that rep. less -> fitness decreased by selection coefficient (s)

Question 5

explain: balancing sleection

Answer 5

• het. geno. favoured
• alleles reach stable equil.
• selective psi acts against homo. geno.

Question 6

name: factors influencing geno. and allele freq. (5)

Answer 6

1. selection
2. mutation
3. gene flow
4. genetic drift
5. inbreeding

Question 7

name: fundamentals of speciation (3)

Answer 7

1. species concept
2. reproductive isolation
3. modes of speciation

Question 8

question: forward mutation rate vs reverse?

Answer 8

• forward (mu) = rate of creating new alleles
• reverse (v) = rate of mutation to OG allele

Question 9

define: gene flow

Answer 9

• mvt. of org. and genes between populations
• can:
  ⤷ introduce new alleles
  ⤷ increase or decrease freq. of existing alleles

Question 10

define: genetic drift

Answer 10

• chance fluctuations of allele freq. due to sampling bias
  ⤷ small changes that occur randomly over time
• especially prominent in small populations

Question 11

explain: inbreeding

Answer 11

• mating between related indiv.
• increases homo. genotypes
• can lead to genotype fixation

Question 12

explain: biological species concept

Answer 12

• group of org. are capable of interbreeding w/ each other but isolated from other species

Question 13

name + explain: modes of speciation (3)

Answer 13

1. allopatric
   - populations diverge due to physical barriers
   - new sp. dev. in separate geo. locations
2. sympatric
   - populations share a territory
   - isolated by genetic, behavioural, temporal, or other barriers
   - prevents gene flow
   - can have allopatric first, and then sympatric when they come back in contact
3. hybrid
   - formation of new sp. due to new hybridization between existing sp.

Question 14

explain: hawaiian drosophila sp.

Answer 14

• relationships of hawaiian sp. consistent w/ geological evidence of island formation
• colonizing new islands = allopatric sp.tion

concept = founder effect
- small population enters into isolated territory
- genetic drift and inbreeding can lead to changes in alleles freq.

Question 15

name (compare): mechanisms of reproductive isolation (2)

Answer 15

1. prezygotic = prevents indiv. from 2 diff. pop./sp. from mating
   - behavioural, gametic, geographic, habitat, mechanical, temporal isolations
2. postzygotic = mem. of 2 pop. can mate but non viable embyro
   - hybrid breakdown, inviability, and sterility

Question 16

explain: kill all hybrids design

Answer 16

• kept two envrt. for two sp. across 6 generations
  ⤷ sympatric bottles = mixed males and females of two sp.
  ⤷ allopatric bottles = males and females of one sp.
• counted progeny in sym. bottles
  ⤷ counted and discarded hybrids
  ⤷ counted parental offspring and used them to make next gen.
• killing hybrids lead to strong selection against interspecies breeding
• shows how social beha. has implications on how pop. reproductively isolate