Wk 11: DNA damage + repair (damage) Flashcards
DNA damage is implicated in which diseases?
- Parkinson’s, alzheimer
- Diabetes
- Atherosclerosis
- Ageing
Which nucleotides are pyrimidine and which ones are purine?
- Pyrimidine: cytosine, thymine + uracil
- Purine: Adenine + guanine
What forms a phosphodiester bond?
Phosphate group of nucleotide joins w/ hydroxyl of adjacent nucleotide
What is deamination?
In aqueous sol 37oC, removes ammonia:
- C -> U
- A -> hypoxanthine
- G -> xanthine
What is depurination?
- Cleavage of glycosyl bond connecting purines to back bone
- Backbone intact
What are depurinated sites called?
Abasic or AP
Give an example of a chemical agent that can alter specific bases within DNA
Reactive oxygen species (ROS)
Give an example of a reactive oxygen species (ROS) and what it can do to specific bases in DNA
Hydroxyl radical
- Reacts w/ guanine to form 8-oxoguanine
- 8-oxoguanine = mutagenic bc pairs w/ adenine not cysteine
What does replication stress give rise to?
Slowing/stalling of replication forks:
- Gives rise to DNA single strand breaks
- Single strand breaks give rise to DNA double strand breaks
What are the main groups of mutations?
- Point mutation
- Frameshift mutation
What is point mutations?
Single aa change: silent, missense + nonsense
What is frameshift mutations?
Insertion/deletion of bases: deletion, insertion, frameshift + non-frameshift
Define silent mutation
No affect on aa sequence
Define missense
New aa substitution
Define nonsense
Stop codon for aa (TAG)
