Topic 7 Flashcards

1
Q

Mutation

A
  • any heritable change in DNA sequence, or DNA compliment (e.g. # of chromosomes)
  • ultimate source of all variation w/in pop’ns
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2
Q

somatic mutations

A
  • mut’ns in somatic cells that are not heritable

- no evolutionary consequence

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3
Q

germline mutations

A

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

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4
Q

chromosomal mutations

A

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
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5
Q

inversions

A

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

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6
Q

point mutations

A

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.

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7
Q

transitions

A

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

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8
Q

transversion

A

substitution of a purine with a pyrimidine and vice versa

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9
Q

Indels

A
  • additions or deletions

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

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10
Q

gene duplications

A
  • often, genes or groups of genes can duplicate
  • important mode of duplication
  • e.g. major histo-compatibility complex (arisen by duplication)
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11
Q

model of recurrent mutation

A
  1. A–>a = u (forward mut’n rate)

2. a–>A = v (back mut’n rate)

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12
Q

Infinite alleles model

A
  • assumes each new mutation creates a new unique allele

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

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13
Q

Stepwise mutation model

A
  • length of alleles incrementally increases or decreases one repeat at a time via mutation
  • gain or lose repeats
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14
Q

deleterious mutation

A

mutations which result in lowered fitness

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15
Q

purifying selection

A

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

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16
Q

3 things which can prevent selection from removing a deleterious mutation

A
  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
17
Q

neutral mutations

A

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
18
Q

nearly neutral mutations

A

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

19
Q

advantageous mutations

A
  • 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
20
Q

mutational load

A
  • 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
21
Q

Effect of a mutation on H-W eq’m

A
  • does not affect H-W eq’m

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