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Cell Proliferation and Underlying diseases > DNA repair and Maintenance of Genome Stability > Flashcards

DNA repair and Maintenance of Genome Stability Flashcards

1
Q

What is a transition mutation?

A

Pyrimidine to Pyrimidine

T->C

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2
Q

What is a transversion mutation?

A

Pyrimidine to purine

T->G

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3
Q

Types of pyrimidine

A

Cytosine

Thymine

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4
Q

Types of purines

A

Adenine

Guanine

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5
Q

What can induce DNA damage

A

UV light

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6
Q

Give an example of when can mutations be advantageous?

A

When the cells only survive in arginine, they can mutate so that you can live without arginine present

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7
Q

What is a nucleotide?

A

A bass + sugar + phosphate backbone

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8
Q

what can point mutations cause?

A

stop codons
silent mutations
point mutations - effects gene function

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9
Q

How is DNA read?

A

triplet codons

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10
Q

What are the consequences of mutations?

A 
Gene amplification
Broken genes 
Fused genes 
Altered genes 
Missing code 
Damaged gene
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11
Q

What causes mutations?

A 
Luck 
Inherited predisposition 
Environmental:
External e.g. smoking 
Internal e.g. free the metabolised oxygen which attack the DNA
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12
Q

Know the types of DNA damage

A

Nucleotide damage (UV light) e.g. pyrimidine dimer
Abasic site (hydrolysis)
Base damage:
- Cytosine deamination e.g. uracil
- Alkylating agents e.g. 06 methyl adenine
- Reactive oxygen e.g. oxoguanine

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13
Q

cause does depurination cause?

A

spontaneous reaction with water

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14
Q

what is the consequence of depurination?

A

base loss

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15
Q

What causes mutations?

A

Replication, a base change does not cause the mutation, it is the replication with the base change

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16
Q

What causes deamination?

A

Spontaneous, specialist deaminases

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17
Q

What is the result of deamination?

A

Mismatch

18
Q

What is the reactive species equation?

A

Oxygen -> Superoxide -> Hydrogen peroxide -> Hydroxyl radical

19
Q

Name the reactive oxygen species which are dangerous

A

Superoxide
Hydrogen peroxide
Hydroxyl radical
Peroxisomes

20
Q

What produces reactive oxygen species?

A

Mitochondria

21
Q

What is the consequence of reactive oxygen species?

A

Base mispair

22
Q

Consequences of UV light?

A

Mispair

23
Q

What does UV form?

A

covalent bonds between adjacent bases between pyrimidine

24
Q

What is the result of reactions with alkalyting agents?

A

loss of base, misread during replication

25
Q

what is the conequences of bulky adducts?

A

non-coding base

26
Q

Why does bulkby adducts cause mutations?

A

body tries to excrete chemicals, cytochrome p450 tries to let you pee them out, makes it more reactive and it is the derivatives of the chemicals which attack your DNA

27
Q

What does alcohol cause?

A

chemicals which interact with both strands of the DNA meaning you cannot pull them apart `

28
Q

Why do mutations happen all of the time?

A

There is not enough genes in the body to encode for all of the functions of the immune system so these genes are segmented because it is confident that it is able to repair them

29
Q

Explain proofreading

A

DNA polymerase adds the wrong nucleotide, it recognises them and goes back to remove them and then able to extend it

30
Q

What is the DNA repair pathway for mis-matched bases?

A

Mismatch repair

31
Q

What is the DNA repair pathway for base damage?

A

Base excision repair

32
Q

What is the DNA repair pathway for nucleotide damage?

A

Nucleotide excision repair

33
Q

What is the DNA repair pathway for DNA breaks?

A

Non-homologous end joining
Microhomology mediated joining
Homologous recombination

34
Q

Describe mismatch repair in eukaryotes

A

There is a nick in the newly synthesised strand
Protein (MSH) binds to the nick and causes it to form a loop
The newly synthesised strand is digested
Insertion of nucleotides to fix the strand

35
Q

Describe mismatch repair in prokaryotes

A

There is a nick in the newly synthesised strand
The old strand is methylated so the protein knows which one the old one is
Protein (MutS) binds to the nick and causes it to form a loop
The newly synthesised strand is digested
Insertion of nucleotides to fix the strand

36
Q

Describe base excision repair

A

The base is removed by glycosylase
Sugar phosphate is removed by AP endonuclease and drp lyase
Gap is filled by polymerase and DNA ligase

37
Q

Describe nucleotide excision repair

A

Pyrimidine dimer - DNA damage recognise
Helicase unwinds the DNA around damage and nucleases cut section of damaged strand 5’ and 3’ to damage
DNA polymerase and ligase

38
Q

Describe non-homologous end joining

A

‘clean break’, ends held together by Ku70/80

DNA ligase joins ends

39
Q

why is non-homologous end joining error prone?

A

there can be a dirty break and this results in loss of base pairs - deletion mutation

40
Q

Describe microhomology end joining

A 
'dirty', non-ligatable ends
DNA ends resect to produce single strand DNA 
Complimentary DNA strands revealed 
Pairing of complimentary ends
Ligated by DNA ligase
41
Q

Describe homologous recombination

A 
Sister chromatids 
CtIP
DNA ends resected to generate single strand DNA
RAD51 
Homology search and strand invasion 
DNA synthesis and branch migration 
'Missing' information replaced 
DNA ligation
42
Q

Example of a DNA repair signature

A

scars

Cell Proliferation and Underlying diseases (12 decks)

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