Zoology 2022 Paper I 50 marks Describe

Q8

(a) Mention the causative agent and means of spread of tuberculosis. Also describe symptoms, diagnosis, treatment and preventive measures of tuberculosis. (20 marks) (b) Explain biological, non-biological and industrial fixation of nitrogen. (15 marks) (c) What is gene therapy? Citing suitable examples explain germline and types of somatic cell gene therapy. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) यक्ष्मा (ट्यूबरक्यूलोसिस) के कारक प्रतिनिधि एवं फैलाव के तरीकों का उल्लेख कीजिए । यक्ष्मा के लक्षणों, निदान, इलाज एवं निवारक उपायों का भी वर्णन कीजिए । (20 अंक) (b) नाइट्रोजन के जैविक, अजैविक एवं औद्योगिक स्थिरीकरण का वर्णन कीजिए । (15 अंक) (c) जीन चिकित्सा क्या है ? उपयुक्त उदाहरण देते हुए जनन वंशक्रम एवं विभिन्न प्रकार की कार्यिक कोशिका जीन चिकित्सा का वर्णन कीजिए । (15 अंक)

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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' in part (a) and 'explain' in parts (b) and (c) demand comprehensive, structured coverage with causal mechanisms and illustrative detail. Allocate approximately 40% of time/words to part (a) given its 20 marks, with 30% each to parts (b) and (c). Structure as: brief introduction → systematic treatment of each sub-part with clear sub-headings → integrated conclusion highlighting biomedical significance. For part (a), cover epidemiology before clinical aspects; for (b), compare the three fixation pathways; for (c), use precise case studies to distinguish germline from somatic approaches.

Key points expected

  • Part (a): Mycobacterium tuberculosis (Koch, 1882) as causative agent; airborne droplet transmission; primary vs post-primary TB; Ghon complex and Simon foci; diagnostic tools including Mantoux test, IGRA, CBNAAT (Indian context), and chest X-ray; DOTS/NDTB programme and MDR-TB/XDR-TB concerns in India
  • Part (b): Biological fixation via nitrogenase enzyme complex (Mo-Fe and Fe-Fe nitrogenases) in Rhizobium-legume symbiosis, Frankia, and cyanobacteria (Anabaena, Nostoc); non-biological fixation via Haber-Bosch process energy requirements and atmospheric lightning; industrial fixation including Ostwald process for nitric acid and fertilizer production statistics
  • Part (c): Definition of gene therapy as therapeutic gene delivery; germline therapy (heritable, ethically restricted, e.g., mitochondrial replacement therapy) vs somatic cell therapy (non-heritable); ex vivo vs in vivo somatic approaches; Indian examples like CAR-T cell therapy development and ocular gene therapy trials
  • Integration: One Health perspective linking TB zoonotic potential (M. bovis), nitrogen cycle disruption and agricultural productivity, plus gene therapy's promise for TB vaccine development and nitrogen-fixing crop improvement
  • Applied context: India's TB elimination target 2025, urea production and import dependency, and regulatory framework for gene therapy under ICMR guidelines

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness22%11Demonstrates precise taxonomic identification (M. tuberculosis complex, acid-fast bacilli), accurate biochemical pathways (nitrogenase reduction of N2 to 2NH3 requiring 16 ATP), and correct molecular mechanisms (viral vectors, CRISPR-Cas9 in gene therapy); distinguishes latent TB infection from active disease; correctly states Haber-Bosch conditions (450°C, 200 atm, iron catalyst)Identifies causative agents and general processes but contains minor errors (confusing M. leprae with M. tuberculosis, oversimplifying nitrogenase mechanism, or conflating germline and somatic therapy boundaries)Major conceptual errors such as attributing TB to bacteria other than Mycobacterium, describing nitrogen fixation as energy-releasing, or defining gene therapy as simply 'genetic engineering' without therapeutic intent
Diagram / labelling14%7Includes well-labelled diagrams for: (a) TB pathogenesis showing Ghon complex with primary lesion, draining lymphatics and lymph node; (b) root nodule structure with infection thread and bacteroid zone; (c) gene therapy vector delivery showing ex vivo vs in vivo pathways with retroviral/adenoviral/AAV integration patternsProvides at least two relevant diagrams with basic labelling but missing structural details (e.g., nodule diagram without zones, gene therapy without vector comparison) or unclear presentationNo diagrams or poorly constructed figures without proper labels; diagrams that misrepresent anatomical or molecular structures significantly
Examples & nomenclature20%10Uses specific nomenclature: M. tuberculosis H37Rv, specific drugs (isoniazid, rifampicin, bedaquiline), nitrogen-fixing organisms (Azotobacter, Clostridium pasteurianum, Trichodesmium), gene therapy cases (Luxturna for RPE65, Zolgensma for SMA, Strimvelis for ADA-SCID); cites Indian initiatives like TB-free India campaign, IFFCO's nano-urea, and ICMR's stem cell registryProvides generic examples without specific strain names, drug combinations, or institutional references; uses common names instead of scientific nomenclatureIncorrect or fabricated examples; confuses nitrogen fixers with nitrifiers; cites non-existent gene therapy trials or misattributes clinical outcomes
Process explanation24%12Elucidates sequential mechanisms: TB's granuloma formation with caseous necrosis and liquefaction; nitrogenase catalytic cycle with Fe-protein and MoFe-protein electron transfer; gene therapy workflow from patient cell harvest through vector transduction to reinfusion; explains why biological fixation is energetically costly yet ecologically essentialDescribes processes in correct order but lacks mechanistic depth (e.g., stating 'bacteria fix nitrogen' without enzyme detail, or 'genes are inserted' without vector explanation)Processes described incorrectly or in illogical sequence; fundamental misunderstanding of how TB evades immunity, how nitrogenase functions, or how therapeutic genes are regulated
Evolutionary / applied context20%10Integrates evolutionary biology: co-evolution of M. tuberculosis with human populations; horizontal gene transfer in nitrogenase evolution; ethical evolution of germline therapy boundaries; connects to India's public health priorities—TB mortality burden, fertilizer subsidy and green revolution legacy, and biotech competitiveness in gene therapy manufacturingMentions applied relevance superficially (e.g., 'TB is a health problem') without evolutionary perspective or specific policy connectionsNo applied context provided; answer remains purely descriptive without linking to disease burden, agricultural sustainability, or therapeutic innovation

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