Molecular Evolution I

Question 1

Describe genetic drift

Answer 1

• stochastic changes in allele frequency due to chance
• rapid changes in small populations, slow changes in large populations

Question 2

Describe positive selection

Answer 2

causes alleles that confer beneficial phenotype to increase in frequency

Question 3

Describe purifying (or negative) selection

Answer 3

causes deleterious alleles to decrease in frequency

Question 4

Selection

Answer 4

reduces genetic diversity

Question 5

Mutations

Answer 5

increase diversity

Question 6

Selection can be defined as

Answer 6

the deterministic loss of low fitness alleles

Question 7

Allozyme surveys revealed

Answer 7

high levels of genetic (allozyme) diversity within populations

Question 8

Give an example of allozyme diversity

Answer 8

frequency of F allele of alcohol dehydrogenase gene decreases at lower latitudes

Question 9

Describe divergence between species

Answer 9

• ‘clock-like’
• under alpha globin amino acid alignment

Question 10

Describe the neutral theory of molecular evolution

Answer 10

• variation within species and divergence between species is chiefly the result of neutral mutations
• genetic drift drives molecular evolution
• explains divergence between species and polymorphism within species

Question 11

Mutation rate

Answer 11

μ/allele/generation

Question 12

Describe population genetics with drift

Answer 12

• alleles have 2 possible fates in finite population: extinction or fixation
• probability of fixation = allele frequency
• for a new mutation, probability of fixation = 1/2N
• neutral mutations can fix by drift in large or small populations

Question 13

Rate of evolution due to drift =

Answer 13

• rate of appearance of mutations x probability of fixation
• 2N x μ x 1/2N
• = μ

Question 14

Neural evolution should occur at

Answer 14

constant rate μ

Question 15

There is so much diversity within populations because

Answer 15

they are large

Question 16

Explain the existence of the molecular clock

Answer 16

neutral mutations fix in species at a rate μ (mutations/time)

Question 17

K =

Answer 17

• 2μt
• where t= time since species diverged from common ancestor