Lecture 12: Molecular Evolution

Question 1

Know how to measure DNA evolution.

Answer 1

Align sequences, measure length, measure differences.

Question 2

How do you calculate divergence?

Answer 2

(number of differences)/ (length of sequences)

Question 3

How do you calculate rate of divergence?

Answer 3

(sequence of divergence)/ (age of common ancestor)

Question 4

What are the patterns of molecular evolution?

Answer 4

• Different nucleotide positions evolve at different rates

- Different genes have different functional constraints this causes different rates of evolution

Question 5

Define genetic load

Answer 5

the presence of unfavorable genetic material in the genes of a population.

Question 6

How does population size and generation time cancel out?

Answer 6

Populations with short generation times tend to have a large Ne (selection is strong, many mutations, few neutral)

Populations with large generation times tend to have a small Ne (selection is weak, few mutations, most neutral)

Question 7

What defines a neutral mutation?

Answer 7

When s < 1/2Ne, a mutation is neutral when it is no longer affectively visible by natural selection

Question 8

What does a dN/sD = 1 indicate?

Answer 8

indicates neutrality

Question 9

What does a dN/sD > 1 indicate?

Answer 9

indicates positive selection

Question 10

What does a dN/sD < 1 indicate?

Answer 10

indicates purifying selection