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Flashcards in SSB + BER1 Deck (23)
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1

What are the 4 different types of base damage?

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

2

What are the 2 different types of sugar damage?

- Hydrogen abstraction
- Oxidation

3

What is deamination and when does it happen?

- Loss an amino group
- Happens during base substitution

4

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

Thymine

5

What is the product of the deamination of Adenine?

Hypoxanthine

6

What is the product of the deamination of Cytosine?

Uracil

7

What is the product of the deamination of Guanine?

Xanthine

8

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

- Thymine is similar to uracil
- Guanine is similar to hypoxanthine

9

Explain the term 'pre-mutagenic'

- 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

What is a point mutation?

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

Which bases are pyrimidines?

Thymine and Cytosine

12

Which bases are purines?

Guanine and Adenine

13

What is a transverse mutation?

Purine --> Pyrimidine
Pyrimidine --> Purine

14

What is a transition mutation?

Purine --> Purine
Pyrimidine --> Pyrimidine

15

What are the 3 most common positions of base alkylation?

- N7MG
- O6MG
- N3MA

16

What is monofunctional alkylation?

When damage is caused in one nucleophilic centre in DNA.

17

Describe spontaneous alkylation

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

18

What is induced alkylation caused by?

Caused by carcinogens found in:
- Tobacco
- Overcooked meat
- Car Exhaust fumes

19

Describe spontaneous base loss

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

20

What is induced base loss caused by?

Environmental alkylation agents such as:
- Aflatoxin
- BPDE

21

What is spontaneous base oxidation caused by?

Cellular metabolites such as ROS.

22

What is induced base oxidation caused by?

- X-Rays
- Cosmic radiation
- Radon

23

Give an example of a base oxidation scenario

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.