Population Genetics 4

Question 1

mutation (2)

Answer 1

• an alteration to the DNA of an organism

- ultimate source of novel genetic variation

Question 2

genetic variance in fitness (3)

Answer 2

• differences in the average fitness of alleles at a locus
• basic fuel upon which evolutions acts in a sexual population
• selection can exhaust variation

Question 3

types of mutations (3)

Answer 3

• point mutation
• structural mutations (deletions, duplications, inversions)
• genomic mutations (haploid -> diploid)

Question 4

mutation rate in DNA replication per generation (3)

Answer 4

• varies from organism to organism
• mutation rate depends on the alleles involved
• in eukaryotes, point mutations occur at a rate of 10^-8 - 10^-10 per basepair per generation

Question 5

forward mutations (2)

Answer 5

• mutations disturbing wildtype function

- symbol: µ

Question 6

back mutations (2)

Answer 6

• mutations restoring wildtype function

- symbol: ν

Question 7

relationship between forward and back mutations

Answer 7

• forward mutations occur at higher rates than backward mutations

Question 8

in haploid populations with only mutation and non selection:

Answer 8

• back mutations replenish variation and prevent fixation, but slowly

Question 9

what effect do mutations have on fitness and selection (2)

Answer 9

• many have no effect or reduce fitness (deleterious)

- selection reduces the frequency of deleterious alleles and mutation continually reintroduces them

Question 10

what happens during mutation with selection in haploids? (2)

Answer 10

• if mutation repeatedly generates deleterious alleles, then they will persist in populations despite their negative effects
• selection will act to remove mutant alleles, but mutation will reintroduce them, with these two forces balancing over time

Question 11

mutation with selection in haploids mean fitness

Answer 11

• with mutation and selection, mean fitness can decline over evolutionary time

Question 12

mutation load (3)

Answer 12

• reduction in fitness due to mutations/mutation rate
• haploid: µ
• diploid: 2µ

Question 13

mutation load and fitness (2)

Answer 13

• mutations reduce fitness on average by an amount that depends only on the mutation rate
• more severe mutations will equilibrate at a lower frequency and less severe mutations at a higher frequency, but the number of deaths will depend only on the mutation rate

Question 14

are mutant alleles expected to be found at a higher frequency when recessive or when non-recessive

Answer 14

• found at a higher frequency when they are recessive than when they affect heterozygous fitness