Botany 2025 Paper II 50 marks 150 words Compulsory Write short notes

Q1

Write short notes on the following in about 150 words each: (a) Nuclear pore complex (10 marks) (b) Epistasis (10 marks) (c) Synaptonemal complex (10 marks) (d) Amphidiploidy (10 marks) (e) Lysosome (10 marks)

हिंदी में प्रश्न पढ़ें

निम्नलिखित में से प्रत्येक पर लगभग 150 शब्दों में संक्षिप्त टिप्पणी लिखिए : (a) केन्द्रक छिद्र सम्मिश्र (10 अंक) (b) प्रभलता (अर्थतरण) (10 अंक) (c) युग्मसूत्री सम्मिश्र (10 अंक) (d) उभयद्विगुणितता (10 अंक) (e) लाइसोसोम (10 अंक)

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Directive word: Write short notes

This question asks you to write short notes. 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 'write short notes' demands concise, information-dense responses for each sub-part. Allocate approximately 30 words per mark, giving roughly 30 words per sub-part. Structure each note as: definition (1 line) → structural/functional details (2 lines) → significance/example (1 line). Spend equal time (~6 minutes) on each part since all carry equal marks. No introduction or conclusion is needed; begin directly with sub-part (a).

Key points expected

(a) Nuclear pore complex: octagonal symmetry, nucleoporins (FG-repeats), Ran-GTP gradient for selective transport, ~125 MDa molecular weight
(b) Epistasis: non-allelic gene interaction, dominant/recessive/recessive epistasis (9:7, 12:3:1, 9:3:4 ratios), complementary gene action in sweet pea (Lathyrus odoratus)
(c) Synaptonemal complex: tripartite structure (lateral elements, central element, transverse filaments), SC protein 1/2/3, zygotene-pachytene stages, recombination nodules
(d) Amphidiploidy: allopolyploid origin, chromosome doubling in F1 hybrid, fertile synthetic species, classic example Raphanobrassica (Karpechenko), Triticum aestivum evolution
(e) Lysosome: acid hydrolases (optimum pH 4.5-5.0), mannose-6-phosphate targeting, autophagy/heterophagy functions, storage diseases (Tay-Sachs, Pompe)

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	25%	12.5	Precise definitions across all five sub-parts: NPC as selective gate not mere pore; epistasis as non-allelic interaction distinct from dominance; SC as protein scaffold not membrane; amphidiploidy requiring genome doubling; lysosome pH specificity and M6P tagging	Broadly correct definitions with minor errors (e.g., confusing epistasis with dominance, calling SC a membrane structure, omitting pH requirement for lysosomal enzymes)	Fundamental misconceptions (e.g., NPC as passive channel, epistasis as mutation effect, lysosome as protein synthesis site)
Diagram / labelling	15%	7.5	At least three well-executed diagrams: NPC cross-section showing cytoplasmic filaments and nuclear basket; SC tripartite structure with CE, LEs, TFs; lysosome with internal pH gradient and hydrolytic enzymes	One or two adequate diagrams with partial labelling, or all five sub-parts described textually without visual aids where diagrams would strengthen response	No diagrams despite structural questions, or diagrams with major structural errors (e.g., showing SC as single line, NPC without octagonal symmetry)
Examples & nomenclature	20%	10	Specific nomenclature: nucleoporins (Nup62, Nup98), SC proteins (SYCP1/2/3), Karpechenko's Raphanobrassica, Indian wheat varieties; epistatic ratios precisely quoted (9:7, 12:3:1, 9:3:4, 13:3, 15:1)	Generic examples (wheat as polyploid without specifying amphidiploid origin), partial ratio recall (9:7 mentioned but not linked to complementary gene action)	No examples, invented ratios, or confused examples (e.g., autopolyploid cited for amphidiploidy, peroxisome functions attributed to lysosome)
Process explanation	25%	12.5	Dynamic processes clearly explained: Ran-GTP cycle for NPC transport; SC assembly/disassembly correlating with recombination; lysosomal enzyme trafficking via Golgi M6P receptors; stepwise amphidiploid formation (hybrid → sterility → chromosome doubling → fertility)	Static descriptions of structures without explaining what happens (e.g., NPC structure described without transport mechanism, SC named without explaining synapsis)	No process explanation, or confused sequences (e.g., lysosomal enzymes synthesized in lysosome, SC forms in diakinesis)
Application / ecology	15%	7.5	Relevant applications: NPC in viral pathogenesis (HIV nuclear entry); epistasis in quantitative trait mapping and crop improvement; amphidiploidy in synthetic crop evolution (triticale); lysosomal storage diseases and enzyme replacement therapy; SC in fertility studies	Brief mention of applications without elaboration, or applications mismatched to sub-parts	No applications mentioned, or irrelevant applications (e.g., ecological succession discussed for cell biology topics)

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