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level: Level 1

Questions and Answers List

level questions: Level 1

QuestionAnswer
Describe point mutationBase 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 themSilent 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 deletionadding 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 functionProtective 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 occurSequence 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 repairProof 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 cancerCancer - 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 testingAccurate and relevant information Breach of confidentiality