Long answer question ( 15 marks ) 1. Describe the denovo - synthesis of purine nucleotides. 2. Explain the metabolic pathway for tge biosynthesis of pyrimidine nucleotides 3. Explain the detail the semi- conservation replication of double standard DNA molecules. Add a note on its repair mechanism. 4. Explain in detail about biosynthesis of proteins? 5. Define mutation ? Explain various types of mutation. Short answer ( 5 marks ) 1. Describe the different DNA repair mechanism? 2. Define genetic code and describe its characterstic feature? 3. What is leading and lagging strands of DNA . 4. Explain the nucleotides? Givr the name of 4 nucleotides. 5. What is onion peel model of DNA replication . Briefly explain. 6. What are okazaki fragments? What is gout?
Summary of All Answers
Long Answer Questions (15 Marks)
| # | Topic | Key Points Covered |
|---|---|---|
| 1 | De novo Purine Synthesis | PRPP synthesis → 5-phosphoribosylamine (committed step, GPAT) → 9 steps to IMP → AMP and GMP; regulation; salvage pathway |
| 2 | Pyrimidine Biosynthesis | CPS II (committed step) → carbamoylaspartate → orotate → OMP → UMP → UTP → CTP; dTMP synthesis; 5-FU and methotrexate |
| 3 | Semiconservative DNA Replication + Repair | Meselson-Stahl; helicase, primase, DNA Pol III, leading/lagging strands, Okazaki fragments, ligase; MMR, BER, NER, NHEJ/HR |
| 4 | Protein Biosynthesis | Transcription → mRNA processing → tRNA charging → initiation (80S complex) → elongation (A/P/E sites, peptidyl transferase, translocation) → termination → post-translational modifications |
| 5 | Mutations | Definition; missense, nonsense, silent, stop-loss, splice-site, frameshift, in-frame, trinucleotide repeats, structural variants; functional classification |
Short Answer Questions (5 Marks)
| # | Topic |
|---|---|
| 1 | DNA Repair: MMR, BER, NER, HR, NHEJ, direct repair |
| 2 | Genetic Code: triplet, degenerate, non-overlapping, continuous, universal, unambiguous, wobble |
| 3 | Leading strand (continuous) vs Lagging strand (discontinuous, Okazaki fragments) |
| 4 | Nucleotides: structure + ATP, GTP, dATP, dTTP |
| 5 | Onion Peel Model: multiple origins, replicons, replication bubbles, sequential firing |
| 6 | Okazaki fragments: mechanism + Gout: pathophysiology, MSU crystals, diagnosis, treatment |