DNA Damage and Repair Flashcards
Name the endogenous sources of DNA damage (internal stressors)
DNA replication errors
DNA recombination errors
Cellular respiration (ROS)
Spontaneous hydrolysis
Name the exogenous sources of DNA damage (external stressors)
Ionising radiation (gamma, x-rays)
Non-ionising radiation (UV)
Chemicals in environment
Compare DNA damage and mutation
Damage - physical changes to normal structure, resulting in mutation or blockage of replication
Mutation - a change in the base sequence of DNA.
What is depurination?
Removal of purine nucleotide, leaving just the sugar/phosphate backbone
Caused by spontaneous hydrolysis
Stalls replication
What is deamination?
Removal of an amino group, resulting in base substitution
Caused by spontaneous hydrolysis
Is mutagenic
What is oxidation of bases?
Oxygen is added to the nucleotide base.
Caused by ROS
Is mutagenic, i.e. results in base substitution (if not removed)
What is base alkylation?
Addition of an alkyl group (by alkylating agents)
Bulky adducts block DNA replication
What is base-analog incorporation?
Chemicals that resemble a DNA base can substitute into the helix. Results in altered base pairing
What are pyrimidine dimers?
Intrastrand linkage between 2 adjacent T’s.
Caused by UV radiation.
Distorts DNA structure impeding replication
What are cross-linking agents?
Cause linkages between the DNA strands.
Prevents DNA strand separation and hence replication
ROS
Reactive oxygen species
Have spare electrons, and so are highly reactive.
Cause DNA damage by interacting with nucleotides
Generated by cell metabolism, radiation
Compare DNA damage to DNA mutation
Damage - changes to the structure, bulky adducts etc.
Mutation - change in base pairing
Causes of double-strand breakages
Radiation
Replication fork stalling and collapse
Physical stress during mitosis
Exogenous damaging agents
