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Flashcards in SSB + BER1 Deck (23)
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1
Q

What are the 4 different types of base damage?

A
  • Substitution
  • Alkylation - adding a methyl group
  • Loss - losing a base due to natural hydrolysis
  • Oxidation - via peroxides
2
Q

What are the 2 different types of sugar damage?

A
  • Hydrogen abstraction

- Oxidation

3
Q

What is deamination and when does it happen?

A
  • Loss an amino group

- Happens during base substitution

4
Q

What is the product of the deamination of 5-methyl cytosine?

A

Thymine

5
Q

What is the product of the deamination of Adenine?

A

Hypoxanthine

6
Q

What is the product of the deamination of Cytosine?

A

Uracil

7
Q

What is the product of the deamination of Guanine?

A

Xanthine

8
Q

Which 4 bases are similar to each-other in base substitution?

A
  • Thymine is similar to uracil

- Guanine is similar to hypoxanthine

9
Q

Explain the term ‘pre-mutagenic’

A
  • When there is DNA damage, it needs to be recognised
  • If the cell goes into S phase before the damage is recognised, it is read as NORMAL
  • This is pre-mutagenic, which can be fixed before the next cell cycle.
10
Q

What is a point mutation?

A

When the cell does not fix the pre-mutagenic base and it continues onto the next cell cycle as if it is not there.

11
Q

Which bases are pyrimidines?

A

Thymine and Cytosine

12
Q

Which bases are purines?

A

Guanine and Adenine

13
Q

What is a transverse mutation?

A

Purine –> Pyrimidine

Pyrimidine –> Purine

14
Q

What is a transition mutation?

A

Purine –> Purine

Pyrimidine –> Pyrimidine

15
Q

What are the 3 most common positions of base alkylation?

A
  • N7MG
  • O6MG
  • N3MA
16
Q

What is monofunctional alkylation?

A

When damage is caused in one nucleophilic centre in DNA.

17
Q

Describe spontaneous alkylation

A
  • When S-Adenosyl Methionine (SAM) forms O6MG
  • O6MG looks like Adenine
  • Therefore it mismatches with Thymine
  • This is a transition mutation
18
Q

What is induced alkylation caused by?

A

Caused by carcinogens found in:

  • Tobacco
  • Overcooked meat
  • Car Exhaust fumes
19
Q

Describe spontaneous base loss

A
  • Caused by the hydrolysis of the N-Glycosyl bond between the sugar and the base
  • Causing depurination and depyrimidation
20
Q

What is induced base loss caused by?

A

Environmental alkylation agents such as:

  • Aflatoxin
  • BPDE
21
Q

What is spontaneous base oxidation caused by?

A

Cellular metabolites such as ROS.

22
Q

What is induced base oxidation caused by?

A
  • X-Rays
  • Cosmic radiation
  • Radon
23
Q

Give an example of a base oxidation scenario

A
  1. Guanine + Oxidation = 8 Hydroxy-Guanine (8HG)
  2. 8HG is similar to Thymine, therefore Adenine is paired with it = Pre- Mutagenic
  3. Another round of replication occurs forming T:A T:A base pairs because it thinks the 8HG is a Thymine so it keeps replicating Thymine.
  4. The 8HG is completely missed = Mutation.