MGD week 3
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8 questions
| 🇬🇧 | 🇬🇧 |
| 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 |