DNA Damage and Repair Flashcards
What is a mutation?
- A mutation is a change in the nucleotide sequence that is heritable
What is meant by wild type DNA?
Standard form of gene
What is a forward mutation?
Wild type gene converted to mutant.
What is a reverse mutation?
Mutant form converted back to wild type.
What is a chromosomal aberration?
A missing, extra or irregular portion of chromosome:
eg deletions, insertions, duplications or inversions
What is meant by monosomy and trisomy? How do they occur?
Monosomy- when an individual is missing one in a pair of chromosomes
Trisomy- when an individual has more than two chromosomes instead of a pair.
Usually occur as an error in cell division.
What are transition and transvehrsion mutations?
Transition- purine swapped for purine and vice versa.
Transversion- purine swapped for pyramiding and vice versa.
What is meant by:
- Silent mutation
- Missense mutation
- Non sense mutation
- Read through mutation
- Silent mutation- no affect on aa sequence
- Missense- results in amino acid substitution
- Non-sense- change amino acid to a stop codon
- Read through- changes stop codon to an amino acid
What is an adduct?
Adduct= a segment of DNA that is bound to a mutagen.
Describe three ways in which DNA can be mutated. (Induced mutations).
- Alkylation of bases
- Crosslinking agents
- Intercalated molecules
How do antioxidants, catalase, peroxidase and superoxide dismutases limit damage to DNA?
Antioxidants- mop up reactive oxygen species
Catalase- catalyses reaction of the decomposition of hydrogen peroxide to water
Peroxidase-catalyses the oxidation of a particular substrate by using hydrogen peroxide
Superoxide dismutases- turn super oxidants into hydrogen peroxide (which is less oxidising and can then be converted into water).
Describe three ways in which DNA can be mutated. (Induced mutations).
- Alkylation of bases
- Crosslinking agents
- Intercalated molecules
What are cyclobutane pyrimidine dimers?
Cross links in DNA between two pyrimidines. Covalently fused dimers formed at adjacent pyrimidines which are bulky lesions and distort the double helix and make errors more likely in transcription and replication.
How can radiation damage DNA?
- Produces hydroxyl radicals from damaging water which in turn damage bases
- Production of clustered lesions (two or more lesions (sites of damage) close to each other) leading to chain breaks.
What is DNA intercalation?
The insertion of molecules between the planar bases of DNA. This can cause single nucleotide insertions and deletions (therefore can block DNA replication and transcription).