Genetic drift

Question 1

What is genetic drift?

Answer 1

Non-adaptive, random genetic changes between generations

Question 2

What are the assumptions of the Hardy-Weinberg theory?

Answer 2

• Either no selection or that selection is constant
• No immigration/emigration
• Negligible effect of mutations
• Population size is large

Question 3

What is the problem with deterministic models of evolution?

Answer 3

• Real world is stochastic

- Chance always intervenes

Question 4

How could non-selective forces lead to the loss of a gene?

Answer 4

Random sampling, especially if sampling is small, can induce variation in gene frequencies between generations
Can loose genes due to a lack of gamete success

Question 5

What conclusions can we draw from genetic simulations?

Answer 5

1. Genetic drift happens more quickly at smaller populations
2. Even in large populations fixation is inevitable but happens over more generations
3. Allele that goes to fixation depends on the initial concentrations in the population
4. Near-neutral genes always become fixed, only mutation/migration causes counter-fixation

Question 6

Why is N not equal to Ne?

Answer 6

Population size not equal to effective population size

• Territorial/sexual selection
• Sex ratio biases towards rarer sex
• Variable fertility
• Negative effect between N & Ne

Question 7

What is the most common way to estimate Ne?

Answer 7

Inferring the number of breeding adults from hypervariable genetic markers

Question 8

When does selection win out over drift?

Answer 8

When 4Ne.S&raquo_space; 1

Question 9

What is the effect of inbreeding?

Answer 9

Causes increase in the frequency of deleterious recessives