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BIOL 202 > Lecture 22 > Flashcards

Lecture 22 Flashcards

1
Q

do most mutations occur in somatic cells or gamete cells?

A

somatic cells

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2
Q

when are mutations inherited?

A

if mutations are in gametes

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3
Q

what percent of offspring carry the mutation if a gamete is mutated?

A

50%

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4
Q

why do only 50% of F1 generation carry mutation from germ-line mutant?

A

mutation occurs randomly so only 1 homologous chromosome will get mutation, so only F1s that inherit that chromosome will have mutation

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5
Q

chromosome mutation VS insertional mutation VS point mutation

A

chromosome mutation: gain/loss of all or part of a chromosome

insertional mutation: insertion of large region of DNA

point mutation: changes in 1 nt

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6
Q

2 categories of point mutations

A
  1. base substitution
  2. indel
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7
Q

2 types of base subtitutions

A
  1. TRANSITION
  2. TRANSVERSION
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8
Q

what is a transition base substitution?

A

purine –> purine
pyrimidine –> pyrimidine

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9
Q

what is a transversion base substitution?

A

pyrimidine –> purine
purine –> pyrimidine

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10
Q

which bases are purine?

A

A and G

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11
Q

which bases are pyrimidine?

A

C and T

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12
Q

4 types of point mutations in ORF

A
  1. Synonymous/Silent Mutation
  2. Nonsynonymous/Missense Mutation
  3. Nonsense Mutation
  4. Frameshift Mutation
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13
Q

what happens in a Synonymous/Silent Mutation?

A

nt sequence changes but aa sequence does not change

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14
Q

what happens in a Nonsynonymous/Missense Mutation?

A

nt sequence changes and changes aa sequence

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15
Q

2 types of Nonsynonymous/Missense Mutations and what they mean

A
  1. conservative –> mutant encodes chemically similar aa
  2. non-conservative –> mutant encodes chemically different
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16
Q

what happens in a Nonsense Mutation?

A

change sequence of codon that codes for an aa into a stop codon

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17
Q

what does the effect of a Nonsense Mutation rely on?

A

depends on the distance from 3’ end of ORF

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18
Q

what does a Nonsense Mutation lead to?

A

triggers nonsense-mediated decay which degrades mRNA

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19
Q

what causes a Frameshift Mutation? and what does it lead to?

A

caused by an insertion or deletion, leading to a change in the translation reading frame for codons downstream of the mutation

20
Q

3 effects of point mutations on gene function

A
  1. WT function
  2. LOF
  3. GOF
21
Q

2 types of LOF and what they mean

A
  1. HYDROMORPHIC: weak/partial function
  2. NULL: non-functional or not produced
22
Q

3 types of GOF and what they mean

A
  1. HYPERMORPHIC: protein is hyperactive
  2. ECTOPIC: more protein made or made in wrong time/place
  3. NEOMORPHIC: protein gains new function
23
Q

where in the genome can point mutations be found?

A

in coding AND non-coding regions

24
Q

example of gene that has LOF after mutation

A

p53

25
Q

example of gene that has GOF after mutation

A

RAS

26
Q

what happens to RAS function with GOF?

A

becomes constitutively active

27
Q

what is the mutation that occurs to make RAS constitutively active?

A

G –> T
Gly –> Val

28
Q

how does mutation cause RAS to become constitutively active?

A

blocks conversion from GTP to GDP so RAS is stuck in active form and cells receive growth signal

29
Q

mutations in non-coding regions affect: (5)

A
  1. transcription
  2. splicing
  3. stability
  4. translation
  5. function
30
Q

2 ways point mutations can affect mRNA splicing

A
  1. make new splice site in wrong place
  2. remove splice site so there is no splicing
31
Q

outcome of PBRM1 mutation on cancer patients

A

PBRM1 mutation causes worse cancer prognosis

32
Q

describe what happens with a BAP1 mutation

A

GGT –> GGG, still Glycine

exon 11 spliced out and causes framshift that makes a stop codon

mRNA and protein are degraded (LOF)

therefore, mutation is silent in coding region but visible in translation

33
Q

what do Northern and Western blots look like if there’s a MISSENSE MUTATION?

A

aa is just swapped, so northern and western blots look the same as WT

34
Q

what do Northern and Western blots look like if there’s a NONSENSE MUTATION?

A

makes early stop codon, so northern looks same as WT but western shows smaller protein OR mRNA degradation via NMD

35
Q

what do Northern and Western blots look like if there’s a FRAMESHIFT MUTATION?

A

can make smaller protein, so northern looks the same as WT but western shows smaller protein OR mRNA degradation via NMD

36
Q

what do Northern and Western blots look like if there’s a REGULATORY REGION MUTATION?

A

northern and western both show no band

37
Q

2 origins of spontaneous mutations

A
  1. errors in DNA replication
  2. chemical changes to DNA
38
Q

2 ways that errors in DNA replication can occur

A
  1. base mispairing
  2. strand slippage
39
Q

what is the DNA pol error rate?

A

300 mutations per mitosis

40
Q

are most DNA pol errors harmful?

A

no, >99% are fixed by DNA repair mechanisms

41
Q

2 types of chemical changes in DNA that lead to mutation?

A
  1. depurination
  2. deamination
42
Q

what happens to DNA if there are no proofreading mechanisms?

A

any mismatch = mutation

43
Q

3 types of errors in base pairing

A
  1. tautomeric base pair
  2. ionized base pair
  3. wobble base pair
44
Q

what is a tautomer?

A

isomaer of a base with diff positions of atoms and their bonds, the forms are in eqb

45
Q

what happens when a thymine base pairs with an enol form of guanine?

A

error in replication causes T-G mismatch

when the DNA is replication, one product will be normal C-G pairing and the mutant product will be A-T pairing

46
Q

when does a mismatch become permanent?

A

once replicated

BIOL 202 (29 decks)

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