Mutations Flashcards

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1
Q

What molecules proof read DNA

A

DNA polymerase

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2
Q

What environmental factors cause mutations?

A

UV - pyrimadines bond to one another
ionising radiation
chemical agents - point mutation, insertion/deletion

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3
Q

Cause of point mutations

A

nitrous acid oxidatively deaminates aromatic primary amines
nitrate
alkylating agents - transversions

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4
Q

Cause of insertion/deletion

A

intercalating agents wedge between bases, distorting DNA helix

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5
Q

Effects of mutation

A

change in DNA = change in RNA
frameshift mutations
polar mutation - affects downstream genes/operons
hydrophobic/hydrophilic AAs formed
chromosomal changes: segmental duplications - recombination, deletion of DNA between duplicates; whole chromosomal duplication

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6
Q

Carcinogenic mutations

A

point mutations can irreversibly alter cellular metabolism, can cause cancer when DNA affected or its repair/replication

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7
Q

Tests for carcinogens

A

Ames test - bacteria that cannot make histidine

Liver enzymes - only carcin. when enzymes try to detoxify

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8
Q

DNA repair methods

A
  1. direct reversal
  2. base excision repair
  3. nucleotide excision repair
  4. mismatch repair
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9
Q

Direct reversal

A

pyramidine dimers via photoreactivation revert to single entities (not in humans)
alkyltransferases reverse base methylation caused by alkylating agents

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10
Q

Base excision repair

A

remove and repair
glycosylases cleave glycosidic bond of corresponding altered nucleotide (on 5’ side by AP endonuclease)
NTs removed by deoxyribose phosphate lyase
gaps filled by DNA polymerase and ligase

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11
Q

Nucleotide excision repair

A

corrects pyrimidine dimers and other lesions causing displacement of bases
NER responds to helix distortions
repair UV and smoke damage

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12
Q

Mismatch repair

A
  1. nonhomologous end-joining: directly joins double-stranded breaks, protein Ku is broken down DNA sensor
  2. homologous end-joining: recombination via 2 Holiday junctions, DNA polymerase fills gaps and ligase seals
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