Q3
(a)(i) Describe the synthetic theory of evolution. (10 marks) (a)(ii) Describe common types of mimicry in insects with suitable examples. (10 marks) (b) Discuss the process of chain elongation during protein synthesis in prokaryotes. (15 marks) (c) Describe the mechanism of ribozyme action and comment on its technological applications. (15 marks)
हिंदी में प्रश्न पढ़ें
(a)(i) विकास के संश्लिष्ट सिद्धांत का वर्णन कीजिए । (10 अंक) (a)(ii) समुचित उदाहरणों के साथ कीटों में अनुहरण के सामान्य प्रकारों का वर्णन कीजिए । (10 अंक) (b) प्राक्केंद्रकी कोशिकाओं में प्रोटीन संश्लेषण के दौरान श्रृंखला दीर्घीकरण की प्रक्रिया की विवेचना कीजिए । (15 अंक) (c) राइबोजाइम क्रिया की क्रियाविधि का वर्णन कीजिए एवं इसके तकनीकी अनुप्रयोग पर टिप्पणी लिखिए । (15 अंक)
Directive word: Describe
This question asks you to describe. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.
See our UPSC directive words guide for a full breakdown of how to respond to each command word.
How this answer will be evaluated
Approach
The directive 'describe' demands systematic, detailed exposition of mechanisms and processes. Allocate approximately 20% (400-500 words) to part (a) covering synthetic theory and mimicry equally, 35% (700-800 words) to part (b) on chain elongation given its 15 marks, and 30% (600-700 words) to part (c) on ribozymes with emphasis on technological applications. Structure with brief introductions for each sub-part, detailed mechanistic bodies with diagrams, and concluding significance statements.
Key points expected
- For (a)(i): Neo-Darwinian synthesis integrating Mendelian genetics, population genetics (Hardy-Weinberg), and natural selection; contributions of Dobzhansky, Mayr, Simpson, and Indian scientist P. Maheshwari on speciation
- For (a)(ii): Batesian mimicry (palatable mimic resembles unpalatable model, e.g., Papilio polytes female mimicking Pachliopta aristolochiae in India), Müllerian mimicry (mutual unpalatability, e.g., Danaus and Euploea), aggressive mimicry (e.g., Photuris fireflies), and automimicry
- For (b): Initiation complex formation, 70S ribosome assembly, charged tRNA entry to A-site, peptidyl transferase activity (23S rRNA), translocation (EF-G/GTP), and termination; contrast with eukaryotic 80S ribosome
- For (c): RNA catalysis via acid-base mechanism, self-splicing introns (Group I and II), RNase P, hammerhead ribozyme structure; technological applications including RNAi therapeutics, synthetic biology, and COVID-19 mRNA vaccine stabilization
- Evolutionary significance: RNA world hypothesis bridging genotypes and phenotypes, molecular basis of evolutionary novelty through gene duplication and neo-functionalization
Evaluation rubric
| Dimension | Weight | Max marks | Excellent | Average | Poor |
|---|---|---|---|---|---|
| Concept correctness | 20% | 10 | Accurately defines synthetic theory components (mutation, recombination, natural selection, genetic drift); correctly distinguishes mimicry types by selective advantage direction; precisely describes elongation factors (EF-Tu, EF-G) and GTP hydrolysis; accurately explains ribozyme catalytic mechanism without confusing with protein enzymes | Basic definitions correct but conflates Batesian/Müllerian mimicry or omits key elongation factors; minor errors in ribozyme mechanism description | Fundamental misconceptions such as Lamarckian elements in synthetic theory, misidentification of mimicry types, confusion between initiation and elongation, or treating ribozymes as protein enzymes |
| Diagram / labelling | 20% | 10 | Includes four clear diagrams: (a)(ii) mimicry comparison with model/mimic/predator; (b) elongation cycle showing A/P/E sites, peptidyl transfer, and translocation with EF-G; (c) hammerhead ribozyme secondary structure and cleavage site; all with precise anatomical/molecular labels and directional arrows | Two to three diagrams present but with incomplete labelling or missing key structural features; hand-drawn quality acceptable but lacks clarity in molecular interactions | Single or no diagram; poorly labelled or irrelevant illustrations; failure to depict dynamic processes (translocation, catalytic cleavage) that are central to the question |
| Examples & nomenclature | 20% | 10 | Indian examples: Papilio polytes mimicry forms in South India; specific naming of elongation factors (EF-Tu, EF-G, EF-Ts) and antibiotics targeting them (tetracycline, streptomycin); ribozyme classes (Group I intron from Tetrahymena, RNase P); scientists credited (Altman, Cech, Nirenberg) | Generic examples without geographic specificity; partial factor naming; omits Nobel laureates or key experimental organisms | No specific examples; invented or incorrect species names; confusion between prokaryotic and eukaryotic factors; failure to mention any technological applications |
| Process explanation | 20% | 10 | Chronological, stepwise exposition: for elongation, details codon-anticodon recognition, proofreading, peptide bond formation chemistry, and ribosome translocation with energy accounting; for ribozymes, explains metal ion cofactors, transition state stabilization, and rate enhancement; temporal sequencing clear throughout | Process described but lacks mechanistic detail; omits energy requirements or proofreading; ribozyme action described phenomenologically without catalytic mechanism | Disorganized sequence; conflates initiation with elongation; no mention of GTP hydrolysis or peptidyl transferase center; treats ribozyme action as magical rather than chemical |
| Evolutionary / applied context | 20% | 10 | For (a): connects synthetic theory to Indian biodiversity hotspots and speciation patterns; for (b): discusses antibiotic resistance evolution targeting elongation factors; for (c): evaluates RNA world hypothesis significance, CRISPR-Cas ribozyme applications, antisense therapeutics, and India's contributions to nucleic acid research (CCMB, IISc work) | Brief mention of evolutionary significance without elaboration; lists applications without evaluation; no Indian research context | No evolutionary context provided; applications omitted or irrelevant; fails to connect molecular mechanisms to organismal biology or biotechnology |
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