Topic 7

Question 1

Mutation

Answer 1

• any heritable change in DNA sequence, or DNA compliment (e.g. # of chromosomes)
• ultimate source of all variation w/in pop’ns

Question 2

somatic mutations

Answer 2

• mut’ns in somatic cells that are not heritable

- no evolutionary consequence

Question 3

germline mutations

Answer 3

-occur in gametes or the cells that produce them and can be passed on to offspring

Question 4

chromosomal mutations

Answer 4

changes in the number or structure of chromosomes

1. inversions: goes from one strand to the other strand (and also rotates 180 degrees)
2. point mutations: a) transitions b) transversion

Question 5

inversions

Answer 5

goes from one strand to the other strand (and also rotates 180 degrees)

Question 6

point mutations

Answer 6

change of a single nucleotide in a DNA sequence

a) Replacement mut’ns (Non-synonymous): mut’ns that change the a.a. in a protein sequence
b) Silent mut’ns (synonymous): do not change the a.a.

Question 7

transitions

Answer 7

substitution of a purine with a purine or a pyrimidine with a pyrimidine
-much more common than transversions

Question 8

transversion

Answer 8

substitution of a purine with a pyrimidine and vice versa

Question 9

Indels

Answer 9

• additions or deletions

- in coding regions: can be highly deleterious –> can disrupt the reading frame

Question 10

gene duplications

Answer 10

• often, genes or groups of genes can duplicate
• important mode of duplication
• e.g. major histo-compatibility complex (arisen by duplication)

Question 11

model of recurrent mutation

Answer 11

1. A–>a = u (forward mut’n rate)

2. a–>A = v (back mut’n rate)

Question 12

Infinite alleles model

Answer 12

• assumes each new mutation creates a new unique allele

- by def’n, all copies of any given allele will be IBD

Question 13

Stepwise mutation model

Answer 13

• length of alleles incrementally increases or decreases one repeat at a time via mutation
• gain or lose repeats

Question 14

deleterious mutation

Answer 14

mutations which result in lowered fitness

Question 15

purifying selection

Answer 15

-selection that acts to remove or lower the frequency of a deleterious mutation

Question 16

3 things which can prevent selection from removing a deleterious mutation

Answer 16

1. continued mutation: keeps pumping it back in
2. dominance effects: e.g. Aa–>hides in heterozygotes
3. genetic drift: when pop’n size is very small

Question 17

neutral mutations

Answer 17

have no effect of fitness

• e.g. silent mutations which do not change an a.a. are typically neutral
• note: silent mutations are not always neutral

Question 18

nearly neutral mutations

Answer 18

have very little effect on fitness (so little that they are effectively neutral)

Question 19

advantageous mutations

Answer 19

• increases the fitness
• they are rare in comparison to deleterious and neutral mutations
• positive selection: sel’n that increases the frequency of advantageous mutations –> reuslts in adaptive evolution

Question 20

mutational load

Answer 20

• caused by mutation selection balance (ignoring drift)
• results in deleterious effects
• load is equivalent to the reductions in the relative pop’n fitness
• basically deleterious alleles hide in heterozygotes

Question 21

Effect of a mutation on H-W eq’m

Answer 21

• does not affect H-W eq’m

- next gen, you have H-W eq’m..but based on the new allele freq’s