1: Finding adaption genes

Question 1

What 4 things do we need to do to measure how diverged subpopulations are from each other?

Answer 1

1. A measure of differentiation
2. An expectation for neutral genes
3. An expectation for genes under divergent selection
4. Ways to sample differentiation of many genes

Question 2

1. Measure of differentiation

If the HWE assumtion of random mating is violated, what will this result in?

Answer 2

Inbreeding = excess of homozygotes

Question 3

1. Measure of differentiation

Describe the Fixation index

Answer 3

• Measure of population differentiation based on the greater probability of mating within than between subpopulations
• Measure of heterozygosity
• S = inbreeding in subpopulations
• T = total population

Question 4

1. Measure of differentiation

What are HT and HS in this equation?

Answer 4

Question 5

(Roughly) What FST values show weak, moderate and strong differentiation?

Answer 5

ROUGHLY
0 - 0.1 = weak differentiation
0.1-0.25 = moderate differentiation
>0.25 = strong differentiation

Question 6

2:An expectation for neutral genes

If theres a barrier between subpopulations, what will happen to FST?

Answer 6

will go up, because over time those allele frequencies in the separate pops. will start to differ more and more from each other (due to genetic drift)

Question 7

What is m, N and Nm?

Answer 7

m = proportion of each subpopulation made up of immigrants in each gen
N = effective size of each subpopulation (if every individual was mating equally and with random mating)
(→ in reality no populations do this, so Ne will always be smaller than the actual consensus size)
Nm = number of migrants each generation

Question 8

3: An expectation for genes under divergent selection

What is s?
And what does this mean for AA in pop 1 and aa in pop 2?

Answer 8

s = Strength of selection

→ AA individuals have a lower fitness in subpop 1
→ aa have a lower fitness in subpop 2

Question 9

When will FST be highest?

Answer 9

Highest FST is when selection is strong, and there’s low migration

Question 10

When will FST be lowest?

Answer 10

Lowest FST when selection is absent and migration is high

Question 11

Fill in the blank

Genes under ——– selection have higher FST than neutral genes

Answer 11

divergent

Question 12

Describe SNPs

Answer 12

One alteration in the bases
Can be coding or non-coding
More common than micro satellites
PCR products can be small
Fewer alleles per locus - need to analyse more loci

Question 13

Fill in the blanks

For neutral loci, FST depends on the balance between —— —– and —— ——. Which is determined by the number of —— (Nm)

Answer 13

For neutral loci, FST depends on the balance betweengene flow and genetic drift. Which is determined by the number of migrants (Nm)