| Describe point mutation | Base substitution
- most common form of mutation
Transition
- change which may not change amino acid
- e.g.) G to C
Transversion
- complete change in amino acid sequence
- e.g) G to A |
| Point mutation may lead to silent mutation or missense mutation or nonsense mutation.
Define them | Silent mutation
- a mutation that does not alter the amino acid specified
Missesne mutation
- a mutation that replaces one amino acid with another
Nonsense mutation
- a mutation the changes the amino acid specified to a stop codon |
| Describe insertion and deletion | adding or deleting base pair
Frame shift
- 1 bp insertion/deletion
No frame shift
- 3 bp insertion/deletion |
| What is purpose of premature termination codons (PTCs) and how does it perform its function | Protective mechanism against mutation
- created from frame shift
- mRNAs with PTCs are degraded by nonsense mediated decay(NMD)
- this is to reduce production of faulty protein |
| Describe how spontaneous and induced mutations may occur | Sequence change in DNA replication
- DNA strand slippage
Chemicals
- nitrous acid replaces amino groups with keto groups
- ethyl methane sulphonate removes purine rings
Exposure to different type of ionising radiation
- UV light, X-ray |
| Describe the process and the role of DNA repair | Proof reading
- polymerase detects and correct it 99% of the times
Nucleotide mismatch repair
- reduces error rate after DNA replication '
- mismatched bases are detected by an enzyme and is is replaced
Base excision repair and Nucleotide excision repair
- repair single stranded DNA damage caused by external agents e.g.) UV or endogenous factors such as reactive oxygen species
- two repair mechanisms are distinct
Double strand break repair
- Happens when both DNA strands are broken which may result in chromosomal rearrangement |
| Explain the relationship between DNA damage and cancer | Cancer
- occurs when DNA repair fails
6 hall marks
- Self sufficiency in growth signals
- insensitivity to anti-growth signals
- avoids apoptosis
- sustained angiogenesis
- metastasis
- tissue invasion
Leads to cancer |
| Explain some of the ethical issues associated with genetic testing | Accurate and relevant information
Breach of confidentiality |
