CK L2 DNA Repair Flashcards Preview

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Flashcards in CK L2 DNA Repair Deck (23)
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1
Q

what is spontaneous deamination

A

the removal of an amino group from a molecule

2
Q

DNA Replication Stress

A

Inefficient replication that leads to replication fork slowing, stalling and/or breakage

3
Q

why is it imortant that spontaneous mismatches get repaired straight away?

A

because it will have a knock on effect during replication where a single mismatch will effect lots once its has been replicated

4
Q

how can DNA replication stress occur?

A

if there is any machinery defects

5
Q

why can lots of errors cause DNA replication stress?

A

because it causes delays which in turn causes stress

6
Q

Types of DNA replication stress

A

> Replication machinery defects
Replication fork progression hindrance
defects in response pathways

7
Q

how can repetitive DNA slow down DNA machinery and cause DNA replication stress

A

Repetitive DNA can lead to fork slippage

8
Q

Fork slippage leads to…?

A

trinucleotide

9
Q

trinucleotide repeat disorders

A

Huntingtons disease

10
Q

trinucleotide repeat disorders- some info on Huntingtons disease

A
> CAG repeats 
> polylgutamine repeats
> normal protein function still unknown 
Mutant protein aggregates in neurons 
> progressive, late onset disease
11
Q

3 different outcomes of DNA damage response

A

> Senescence
Proliferation
Apoptosis

12
Q

Senescence is…?

A

permanent cell cycle arrest

13
Q

Apoptosis

A

Cell death

14
Q

if DNA damage levels too high or persist what are the two outcomes

A

> Senescence

> Apoptosis

15
Q

Proliferation…?

A

DNA repair

16
Q

what do cell cycle checkpoints do?

A

slow dow the cell cycle to allows for DNA repair

17
Q

the 4 steps in base excision repair

A

1) deamination converts one base into another e.g C into U (this is the error)
2) U is detected and removed leaving base-less nucleotide
3) Base-less nucleotide is removed leaving small hole in DNA backbone
4) The hole is filled with the right base by a DNA polymerase and the gap is sealed by ligase

18
Q

what is a dimer

A

two identical subunits

19
Q

4 steps of Nucleotide excision repair

A

1) UV radiation produces a thymine dimer
2) once the dimer has been detected the surrounding DNA is opened to form a bubble
3) enzymes cut the damaged DNA region out of the bubble
4) a DNA polymerase replaces the excised (cut-out) DNA and a ligase seals the backbone

20
Q

4 steps of mismatch repair

A

1) a mismatch is detected in newly synthesised DNA e.g G paired with T.
2) the new DNA strand is cut and the mispaired nucleotide and its neighbours are removed by exonuclease activity
3) the missing patch is replaced with correct nucleotides by a DNA polymerase
4) a DNA ligase seals the gap in the DNA backbone

21
Q

info on single strand breaks

A

> relatively simple
many diff mechanisms
integrity of DNA molecule intact
damage removed on one strand only
homology of other strand used to repair
not error-free but not error prone either

22
Q

info in double strand breaks

A

> complex
integrity of DNA molecule lost
more likely to be error prone
use of homology may be possible

23
Q

what are the two ways of repairing a double strand break?

A

1) non-homologous end joining

2) homologous directed repair