HWE: Non-random mating - 12

Question 1

What are the 3 types of mating

Answer 1

1. outcrossing
2. inbreeding
3. assortative mating

Question 2

Define outcrossing

Answer 2

individuals related tend to avoid each other, non-random because deliberately avoiding each other

Question 3

Define inbreeding

Answer 3

selfing in plants or mating with relatives.
includes consanguineous mating = mating between those that share a common ancestor/the same blood

Question 4

Define assortative mating

Answer 4

where individuals choose mates that are similar (positive) or dissimilar (negative) in phenotype

Question 5

What are the two conclusions of HWE

Answer 5

1. that allele frequencies don’t change 2. that allele frequencies can be used to calculate genotype frequencies (through the equation)

Question 6

How does inbreeding change the allele and genotype frequencies

Answer 6

allele frequencies don’t change, but genotype frequencies do, causing an increase in both homozygotes and a decrease in heterozygotes. This is because heterozygotes that self with themselves produce 1:2:1

Question 7

What HWE assumption do the results of inbreeding violate

Answer 7

that allele frequencies can be used to calculate genotype frequency

Question 8

Can non-random mating on its own result in evolution

Answer 8

no (ex. needs force of selection)

Question 9

What is the inbreeding coefficient (F)

Answer 9

F = probability that two alleles are identical by descent
F = 0 no inbreeding
F = 1 selfing (only homozygotes), 0.5 (heterozygotes)

Question 10

How to calculate probabilities of alleles being passed down

Answer 10

And = multiple
Or = add

Question 11

define inbreeding depression (delta)

Answer 11

lower fitness in inbred populations because of increase in homozygosity and therefore increased expression of recessive alleles and recessive alleles are commonly deleterious

Question 12

What does a positive or negative delta for inbreeding depression mean

Answer 12

negative delta = inbred individuals have a higher fitness (uncommon)
positive delta = outbred individuals have a higher fitness

Question 13

Why is inbreeding bad (2)

Answer 13

increases frequency of deleterious alleles and decreases genetic variation

Question 14

What are factors that lead to inbreeding (3)

Answer 14

decreased population size or density
isolation
hybridization and polyploidy

Question 15

How can inbreeding be reduced (3)

Answer 15

migration
captive breeding (deciding who breeds with who)
inbreeding avoidance

Question 16

What are 3 ways of inbreeding avoidance

Answer 16

mate choice (ex. MHC gene used to recognize if two individuals are closely related)
self-incompatibility genes (inability to produce zygotes after self pollination)
dispersal
(small population avoidance may not be possible)

Question 17

What are the short and long term results of drift, migration, and inbreeding

Answer 17

short term = increased homozygosity due to drift or inbreeding can expose deleterious recessive alleles
long term = alleles are lost via drift which reduces the ability to adapt (to go or bad)

Question 18

Ex. a reduce in heterozygous frequency is seen in one population of sea otters compared to the others, what are 3 possibilities for this heterozygote deficit

Answer 18

1. inbreeding (assortative mating) 2. heterozygote inferiority 3. hidden population structure

Question 19

Explain how assortative mating can cause heterozygote deficit

Answer 19

AA x AA = AA
aa x aa = aa
Aa x Aa = 1:2:1
homozygotes will increase and heterozygotes will decrease

Question 20

Explain how heterozygote inferiority can cause heterozygote deficit

Answer 20

the homozygotes have a higher survival rate that could be due to a difference in phenotype or genotype quality

Question 21

Explain how hidden population structure can cause heterozygote deficit

Answer 21

Wahlund Effect
Although different genotypes are living in the same area, for some reason they still aren’t breeding together and random mating isn’t occurring. The same phenotypes are mating with one another and there is a hidden population structure!