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Cell And Molecular Yr 2 > DNA repair > Flashcards

Flashcards in DNA repair Deck (19)
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1
Q

ways that DNA molecules effected by chemical change

A

Thermal degradation (heat/water)

Metabolic byproducts (oxidation)

Environmental substances (benzopyrene)

Radiation (UV, nuclear fission)

2
Q

Difference between purine and pyrimidine

A

G and C (3 h bonds)
T and A and U (2 bonds)
G and A double ring purines
T and C single ring pyrimidine

3
Q

difference between transition and transvehrsion mutations

A

transition - double ring for double ring or single for single

transversion - single for double vice versa

transition more likely and doesn’t often cause change in AA

4
Q

Uv light causes…

A

formation of pyrimidine dimers

5
Q

what is a pyrimidine dimer

A

two T or C connect together forming protrude of backbone, cannot replicate easily

6
Q

what can cause Double stranded DNA breaks

A

ionising radiation, free radicals/ oxidation, replication errors

7
Q

what is deamination

A

hydrolysis of C. to U releasing ammonia

8
Q

what is depurination

A

glycosidic bond hydrolysed releasing A OR G

9
Q

how do free radicals cause DNA damage

A

attack both bases and backbone
carcinogenic
they steal electrons from DNA by oxidation

10
Q

when is base excision repair required

A

following oxidation, deamination and alylation

11
Q

steps in base excision repair

A
  1. cleave the inccorrect tase by DNA glycosylase
  2. AP endonuclease and phosphodiesterase remove the backbone (sugar phosphate)
  3. DNA polymerase adds new nucleotide
  4. ligase seals nick
12
Q

How do the glycosylases identify errors in DNA

A

use the base flipping strategy

13
Q

What is nucleotide excision repair used for

A

to remove pyrimidine dimers

14
Q

steps in nucleotide excision repair

A
  1. Excision nuclease removes section of ssDNA
  2. DNA helicase unwinds DNA and pulls away from strand
  3. polymerase and ligase fill in the gaps with correct sequence
15
Q

what and how is translational DNA polymerase used. what a re the disadvantages

A

recruited by the sliding clamp to remove covalent modifications and to synthesise
it is not as precise and doesn’t proof read as well so can get single base changes mutations

16
Q

2 mechanisms used to repair dsDNA damage

A

non homologous End joining

and

homologous recombination

17
Q

steps in non homologous End joining

A
  1. end recognition by Ku Heterodimers
  2. additional portions, DNA-PK and ATM protein kinases attach
  3. repair synthesis and ligation
18
Q

steps in homologous recombination

A
  1. using sister chromatid
  2. digestive 5’ end using nuclease
  3. unwind sister and use as template
  4. go back to original complimentary strand
  5. DNA ligation
19
Q

what occurs if issue with. homologous recombination

A

cause cancers and diseases