Theme 4B

Question 1

What is a population?

Answer 1

Interbreeding group of individuals that belong to the same species and live within a restricted geographical area

Question 2

What are population genetics?

Answer 2

Consequences of Mendelian Genetics in a population - shift from Individual- to Population- Level Thinking

Question 3

What is the null hypothesis for evolution?

Answer 3

If evolution is changes in allele frequencies over time, then null hypothesis should be no change in allele frequencies over time

Question 4

Genetic Diversity in the Absence of Evolution Model

Answer 4

1. A single locus with two alleles does not change state b/w generations, i.e., no mutation
2. Alleles are not added to the population: No gene flow from other populations
3. The population is very big (infinite in theory) -> eliminates the effect of random processes that could change allele frequencies
4. Natural selection does not affect the alleles considered, regardless of their genotype at the locus of
   interest, all diploid individuals have the
   same fitness
5. Random mating: all diploid individuals have the
   same fitness

Question 5

What is Genetic Drift?

Answer 5

Allele frequencies can change by chance alone given the number of matings that can occur when you have a low number of individuals compared to a large number of individuals

Question 6

Hardy-Weinberg equilibrium

Answer 6

Population allele frequencies do not change if:

• There is no mutation
• There is no migration (gene flow)
• Population is infinitely large
• Genotypes do not differ in fitness (no selection)
• Mating is random

Question 7

Genotypes and Frequencies According to HWE

Answer 7

AA = p^2
Aa = 2pq
aa = q^2

Question 8

Because the gametes are haploid, and mix RANDOMLY:

Answer 8

if there is no selection at the genotype level, all gametes go back into gene pool

Question 9

Even if a population is not in HWE, one round of random mating with the other conditions met will:

Answer 9

Return the population to equilibrium

Question 10

Why is HWE a powerful test in evolution?

Answer 10

• HWE tells us when Evolution is NOT occurring – null model or hypothesis in evolution
• Departure from equilibrium suggests that one or more of the assumptions has been violated (i.e., evolution)
• Use HWE to predict genotype frequencies when we have less information about a population

Question 11

In general, in a sample of n individuals, the frequency of an allele is:

Answer 11

The number of occurrences of the allele divided by twice the number of individuals in the sample (2n).