Zoology 2023 Paper II 50 marks Describe

Q2

(a) Give structure of t-RNA. Write role of different RNAs in the translation process. (20 marks) (b) Describe the principle and method of whole animal cloning. (15 marks) (c) Explain Stanley Miller experiment. In which way, it provided support to most acceptable theory of origin of life? (15 marks)

हिंदी में प्रश्न पढ़ें

(a) टी-आर.एन.ए. की संरचना दीजिए। अनुवाद प्रक्रिया में विभिन्न प्रकार के आर.एन.ए. की भूमिका के बारे में लिखिए। (20 अंक) (b) संपूर्ण पशु क्लोनन (क्लोनिंग) के सिद्धांत एवं इसकी विधि का वर्णन कीजिए। (15 अंक) (c) स्टैनले मिलर के प्रयोग की व्याख्या कीजिए। जीवन की उत्पत्ति के सर्वाधिक स्वीकार्य सिद्धांत को इसने किस प्रकार से समर्थन प्रदान किया? (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' demands detailed, systematic exposition of structures and processes. Allocate approximately 40% of time/words to part (a) given its 20 marks, with 30% each to parts (b) and (c). Structure: brief introduction linking molecular biology to evolutionary biology; body with three clearly demarcated sections for each sub-part; conclusion synthesizing how these three domains—translation machinery, reproductive biotechnology, and prebiotic chemistry—represent hierarchical levels of biological organization from molecules to organisms.

Key points expected

  • Part (a): Cloverleaf secondary structure of t-RNA with DHU loop, TΨC loop, anticodon loop, and acceptor stem; 3D L-shaped tertiary structure stabilized by modified bases and hydrogen bonds
  • Part (a): Functional roles of m-RNA (template), t-RNA (adaptor/charging), r-RNA (catalytic/structural component of ribosome), and small RNAs in translation initiation/termination
  • Part (b): Principle of nuclear transfer/cloning based on genomic totipotency and epigenetic reprogramming; distinction between reproductive and therapeutic cloning
  • Part (b): Methodological steps: enucleation of recipient oocyte, fusion with donor somatic cell, activation, culture to blastocyst, and embryo transfer; mention of Dolly (1997) and Indian examples like Garima II buffalo cloning at NDRI, Karnal
  • Part (c): Miller-Urey apparatus details: reducing atmosphere (CH₄, NH₃, H₂, H₂O), electric discharge as energy source, condensation and trapping system
  • Part (c): Synthesis of amino acids (glycine, alanine), hydroxy acids, and other organic compounds; support for Oparin-Haldane primordial soup hypothesis and chemical evolution preceding biological evolution

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Precise description of t-RNA cloverleaf and L-shaped structures with correct loop nomenclature; accurate explanation of somatic cell nuclear transfer mechanism; correct identification of reducing atmosphere composition in Miller-Urey experiment and its alignment with Oparin-Haldane theoryBasic structural features mentioned but with errors in loop names or missing tertiary structure; general cloning principle stated but method confused with embryo splitting or parthenogenesis; Miller experiment described but atmosphere composition incorrect or theory linkage vagueFundamental misconceptions such as confusing t-RNA with m-RNA structure; cloning described as genetic engineering or IVF; Miller experiment conflated with Urey's later work or wrong energy source cited; no clear connection to chemical evolution theory
Diagram / labelling20%10Clear, proportionate diagrams for (a) t-RNA cloverleaf with all loops and modified bases labelled, (b) nuclear transfer procedure showing micromanipulation, and (c) Miller-Urey apparatus with all components; neat presentation with accurate biochemical symbolsDiagrams attempted for at least two parts with partial labelling; t-RNA missing 3D representation or incorrect base pairing shown; cloning diagram confused with IVF; Miller apparatus missing condenser or trapNo diagrams or very poor sketches without labels; diagrams chemically/biologically inaccurate; failure to recognize that visual representation is essential for this question type
Examples & nomenclature15%7.5Specific examples: Dolly (Finn Dorset × Scottish Blackface), Indian cloned animals (Garima II buffalo, Samrupa cow at NDRI); correct nomenclature: DHU/ψ, TΨC, CCA-3' end, aminoacyl-tRNA synthetases, enucleation, electrofusion, cumulus cells; modified bases named (inosine, pseudouridine, dihydrouridine)Dolly mentioned without breed details; general reference to 'cloned animals' without Indian examples; some modified bases named but not linked to specific loops; technical terms used with minor errorsNo specific examples; generic terms like 'sheep' or 'cow' without naming; incorrect nomenclature (e.g., 'cloning genes' instead of nuclear transfer); failure to use standard biochemical terminology
Process explanation25%12.5Stepwise, logical exposition: for (a) t-RRNA charging and ribosomal dynamics during translation; for (b) complete SCNT protocol with epigenetic reprogramming challenges; for (c) sequential chemical reactions in Miller-Urey with condensation, polymerization implications; clear cause-effect relationships throughoutProcesses described but sequence unclear or steps missing; translation roles stated without temporal coordination; cloning steps jumbled; Miller experiment as static description without reaction sequence; some mechanistic gapsNo coherent process description; random facts listed without logical flow; failure to distinguish between principle and method; experimental procedure described as results only; inability to explain 'how' things occur
Evolutionary / applied context15%7.5For (a): RNA world hypothesis connection, evolutionary conservation of t-RNA structure; for (b): ethical dimensions, conservation applications (cloning endangered species like Gaur 'Noah'), agricultural implications for India; for (c): transition from chemical to biological evolution, limitations of Miller-Urey (atmosphere debate, Fox's proteinoid microspheres as extension)Brief mention of RNA world or cloning ethics without elaboration; some recognition that Miller experiment relates to origin of life but no discussion of subsequent criticisms or alternative hypotheses (hydrothermal vent theory)No evolutionary or applied context; answer remains purely descriptive without synthesis; failure to connect molecular biology to organismal biology or to address why these topics matter; no mention of ethical, conservation, or theoretical implications

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