Botany 2021 Paper II 50 marks Describe

Q3

(a) Describe properties of genetic code and briefly explain Wobble hypothesis. 15+5=20 (b) What are the characteristic features of Cytoplasmic inheritance ? Describe the role of chloroplast and mitochondrial genes in this inheritance. 7+8=15 (c) Discuss the biosafety concerns of transgenic plants. 15

हिंदी में प्रश्न पढ़ें

(a) आनुवंशिक कूट के गुणों का वर्णन कीजिए तथा वॉबल परिकल्पना की संक्षेप में व्याख्या कीजिए । 15+5=20 (b) कोशिकाद्रव्य वंशानुक्रम की विशेषताएं क्या हैं ? इस वंशानुक्रम में हरितलवक (क्लोरोप्लास्ट) एवं माइटोकॉन्ड्रियल जीनों की भूमिका का वर्णन कीजिए । 7+8=15 (c) पराउपतिमूलक (ट्रांसजेनिक) पौधों की जैव-सुरक्षा चिंताओं की विवेचना कीजिए । 15

Evaluate your answer to this question → See all 2021 Botany questions

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 comprehensive coverage with precise details. Allocate approximately 40% time/words to part (a) given its 20 marks, 30% each to parts (b) and (c). Structure: brief introduction on genetic information flow; body with three clearly demarcated sections for each sub-part; conclusion synthesizing how understanding genetic code and cytoplasmic inheritance informs responsible transgenic development. Use diagrams strategically in (a) and (b).

Key points expected

  • Part (a): All seven properties of genetic code (triplet, degenerate, non-overlapping, commaless, non-ambiguous, universal, specific start/stop codons) with brief elaboration; Wobble hypothesis explaining flexibility at third codon position, Crick's rules, and tRNA anticodon pairing
  • Part (a): Diagram showing codon-anticodon pairing with wobble position highlighted, or table illustrating wobble base pairing rules (G-U, I-U/C/A pairing)
  • Part (b): Four key features of cytoplasmic inheritance—maternal/uniparental transmission, absence of Mendelian segregation, reciprocal cross differences, phenotypic expression in all progeny; specific roles of chloroplast genes (photosynthesis, herbicide resistance like atrazine resistance in Solanum) and mitochondrial genes (cytoplasmic male sterility, maternally inherited diseases)
  • Part (b): Examples of cytoplasmic inheritance—leaf variegation in Mirabilis jalapa (Correns), chloroplast inheritance in Oenothera, mitochondrial male sterility in maize (T-cytoplasm) and its Indian relevance in hybrid seed production
  • Part (c): Biosafety concerns categorized—gene flow to wild relatives (e.g., Bt cotton in India), development of resistance in target pests, non-target effects on beneficial insects, allergenicity/toxicity of novel proteins, horizontal gene transfer risks, and impact on biodiversity and traditional farming systems
  • Part (c): Regulatory frameworks—Cartagena Protocol, Indian EPA 1986 rules, GEAC functions; mention specific Indian cases like Bt brinjal moratorium and farmer suicides debate, concluding with need for case-by-case risk assessment and public participation

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness22%11All seven genetic code properties accurately stated with correct definitions; Wobble hypothesis precisely explained with Crick's 1966 rules; cytoplasmic inheritance features correctly distinguished from nuclear inheritance; chloroplast and mitochondrial gene functions accurately described; biosafety concerns scientifically grounded without exaggeration or dismissalMost properties mentioned but some definitions incomplete or confused (e.g., degeneracy vs ambiguity); Wobble hypothesis oversimplified; cytoplasmic inheritance features listed without clear distinction; gene roles vaguely stated; biosafety concerns generic without mechanistic basisMajor conceptual errors—confusing genetic code properties, misrepresenting Wobble as mutation, equating cytoplasmic with sex-linked inheritance, or presenting biosafety as purely political issue without scientific foundation
Diagram / labelling16%8Clear self-drawn diagram for (a) showing codon-anticodon pairing with wobble position at third base, or genetic code table with start/stop codons highlighted; for (b) schematic showing maternal inheritance pattern or organelle genome organization; proper labelling with biochemical notations (e.g., inosine in wobble position)Diagrams present but incomplete labelling, missing key features like wobble base pairing rules, or generic organelle diagrams without inheritance pattern illustration; printed text descriptions substitute for visual representationNo diagrams despite clear visual demand; or seriously flawed diagrams with incorrect pairing (e.g., A-A instead of A-U), wrong organelle structures, or illegible labelling
Examples & nomenclature18%9Specific nomenclature: Nirenberg, Matthaei, Khorana for code elucidation; Crick for wobble; Correns, Baur, Chargaff for cytoplasmic inheritance; specific genes—rbcL, psbA (chloroplast); cob, cox (mitochondrial); Indian examples—Bt cotton (MECH-162), Bt brinjal (Event EE-1), TERI's transgenic mustard; regulatory bodies—GEAC, RCGM, Cartagena ProtocolSome examples mentioned but lacking specificity—generic 'Bt crops' without event names, 'some plants' for cytoplasmic inheritance without species, international protocols unnamed; scientists mentioned without clear contribution attributionNo specific examples or incorrect attribution; invented gene names or events; confusing cytoplasmic male sterility with genic male sterility; irrelevant examples from animal biotechnology
Process explanation22%11Wobble mechanism explained stepwise—standard Watson-Crick pairing at first two positions, non-standard at third; tRNA conformational flexibility and inosine modification; cytoplasmic inheritance mechanism—organelle segregation during oogenesis, pollen exclusion of plastids; biosafety assessment process—confined field trials, environmental release monitoring, gene flow quantification methodsProcesses described in static terms without dynamic mechanism; wobble mentioned as 'flexibility' without structural basis; cytoplasmic inheritance as 'passed through egg' without explaining organelle exclusion; biosafety as list of concerns without assessment methodologyNo mechanistic explanation; confusing process with outcome; or entirely missing process components (e.g., describing wobble as random mutation, cytoplasmic inheritance as 'in cytoplasm' without transmission mechanism)
Application / ecology22%11Integration across parts: genetic code understanding enables transgene design (codon optimization for host expression); cytoplasmic inheritance applied to CMS-based hybrid seed production (e.g., rice WA-CMS, sorghum A1 lines in India); balanced biosafety discussion recognizing both benefits (reduced pesticide use in Bt cotton) and risks (resistance management, refuge strategy); policy recommendations grounded in Indian agricultural contextApplications mentioned separately without integration; CMS noted as 'useful' without explaining hybrid production mechanism; biosafety concerns listed without balancing benefits or specific Indian regulatory context; generic global statements without local relevanceNo application dimension; or uncritical promotion/demonization of transgenic technology; complete disconnect between theoretical parts (a)-(b) and applied part (c); irrelevant digression into general biotechnology

Practice this exact question

Write your answer, then get a detailed evaluation from our AI trained on UPSC's answer-writing standards. Free first evaluation — no signup needed to start.

Evaluate my answer →

More from Botany 2021 Paper II