Cellular response to DNA Damage and Repair Flashcards Preview

Biochemistry 431 > Cellular response to DNA Damage and Repair > Flashcards

Flashcards in Cellular response to DNA Damage and Repair Deck (21):
1

What type of DNA damage does Base Excision Repair take care of?

DBSC; Depurination, Base Oxidation, Single-stranded break, or cytosine deamination.

2

How are double stranded breaks repaired?

Double Stranded Break Repair. or non-homologous end joining.

3

Thymine Dimers

UV light introduces thymine dimers (Fixed by nucleotide excision repair)

4

What type of DNA damage does Nucleotide Excision Repair take care of

Thymine Dimers and Bulky Adducts.

5

Base Mismatch

wrong base is attached to each other (Fixed by Mismatch repair)

6

How is base alkylation repaired?

Direct Reversal.

7

How do point mutations occur?

Mispairing; insertion of base analogs, or chemical mutagens (Nitrous acid, hydroxylamine and alkylating agents)

8

How do DNA mutations occur (3)

1) Mistakes during DNA replication 2) DNA subject to spontaneous damage (Deamination or Depurination) 3) Induced damage can lead to mutations caused by environmental agents (Chemical mutagens, UV radiation)

9

Oxidative Deamination

1 ) C to U (Now pairs with A) 2) A to hypoxanthine (now pairs with C) 3) G to Xanthine ( still pairs with C) 4) 5-methylcytosine to Thymine.

10

8-Oxoguanine

Produced when guanine is oxidized; base pairs with Adenine now.

11

Alkylation

Methylation; Guanine goes to O5-methyl guanine; binds with T, when guanine should bind with C

12

Oxygen Radical Damage

Breaks sugar rings

13

Spontaneous Base Loss

Glycosyl bond linking DNA bases with deoxyriboes is labile under physiological condition. Loss of a purine or pyrimidine base creates an apurinic or apyrimidic site. Happens through hydrolysis.

14

Nitrous acid

HNO2 Causes Oxidative deamination

15

Intercalating agents

Ethidium bromide, acridine orange) distort the helic causing frameshift mutations.

16

How does Ethidium Bromide and other intercalating agents work?

They stack in between bases (Aided by their planar goups) , and causes issues with DNA polymerase. Introduces frameshift mutations by the addition or removal of bases.

17

UV induced pyrimidine dimers

UV light causes condensation of ethylene groups. Causes distortion in the backbone.

18

What enzyme repairs methylated guanine?

O6-methylguanine-DNA methyltransferase

19

What enyme repairs methylated adenine and cytosine?

AlkB

20

UvrAB

DNA scanner in Nucleotide Excision Repair Scanner. Made mobile by ATP hydrolysis

21

Mismatch repair in E.Coli is dependent on______

DNA methylation

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