Botany 2023 Paper II 50 marks 150 words Compulsory Write short notes

Q1

Write short notes on the following in about 150 words each : 10×5=50 (a) Cell-cell adhesion mechanism 10 (b) Structure and functions of cytoskeleton 10 (c) Characteristics of triplet codon 10 (d) Crossing over and its significance 10 (e) Correlation, its types and significance 10

हिंदी में प्रश्न पढ़ें

निम्नलिखित में से प्रत्येक पर लगभग 150 शब्दों में संक्षिप्त टिप्पणियाँ लिखिए : 10×5=50 (a) कोशिका-कोशिका आसंजन क्रियाविधि 10 (b) कोशिकापंजर की संरचना एवं कार्य 10 (c) त्रिक कोडोन के अभिलक्षण 10 (d) विनिमय (क्रॉसिंग ओवर) एवं इसका महत्व 10 (e) सहसंबंध, इसके प्रकार एवं महत्व 10

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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 coverage of all five sub-parts within strict word limits. Allocate approximately 30 words per sub-part (150 words total), spending roughly equal time on each since all carry equal marks. Structure each sub-part as: definition (1 line) → key features/mechanism (2-3 lines) → significance/function (1-2 lines). No elaborate introduction or conclusion is needed; prioritize technical precision and syllabus-aligned terminology over narrative flow.

Key points expected

(a) Cell-cell adhesion: Cadherin-mediated calcium-dependent adhesion; selectins, integrins, and immunoglobulin superfamily roles; adherens junctions, tight junctions, and desmosomes as structural manifestations
(b) Cytoskeleton: Three components—microfilaments (actin, 7nm), intermediate filaments (keratin/vimentin, 10nm), microtubules (tubulin, 25nm); functions in cell shape, motility, intracellular transport, and chromosome segregation
(c) Triplet codon: Non-overlapping, degenerate, unambiguous nature; 64 codons for 20 amino acids with 3 stop codons (UAA, UAG, UGA); wobble hypothesis explaining degeneracy; universality with minor mitochondrial exceptions
(d) Crossing over: Occurs during pachytene of prophase I; chiasma formation and terminalization; Holliday junction model; significance in recombination, genetic diversity, and linkage mapping
(e) Correlation: Positive, negative, and zero correlation types; Pearson's r coefficient range (-1 to +1); significance in plant breeding selection indices and ecological association studies

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	25%	12.5	Demonstrates precise understanding across all five sub-parts: correctly identifies cadherin-catenin complexes in (a), distinguishes all three cytoskeletal elements by protein composition and diameter in (b), accurately states codon properties and wobble position in (c), correctly places crossing over in pachytene with chiasma terminalization in (d), and properly defines correlation coefficient range in (e)	Shows generally correct concepts with minor errors: confuses tight junctions with gap junctions in (a), omits intermediate filaments or misstates microtubule diameter in (b), states degeneracy without explaining wobble in (c), places crossing over in diplotene in (d), or conflates correlation with regression in (e)	Contains fundamental conceptual errors: describes adhesion as purely physical without protein mediators in (a), fails to identify any cytoskeletal component correctly in (b), describes codon as overlapping or doublet in nature in (c), confuses crossing over with independent assortment in (d), or describes correlation as causation in (e)
Diagram / labelling	15%	7.5	Includes at least 2-3 quick schematic diagrams where most valuable: cadherin domain structure or junction types in (a), cytoskeletal element comparison or spindle apparatus in (b), codon-anticodon pairing with wobble position in (c), chiasma formation stages in (d), or scatter plot representation in (e); all with clear, accurate labels	Provides one diagram with partial labelling, or mentions diagrams without actually drawing them ('see figure showing...'); labels may be incomplete or slightly misplaced	No diagrams attempted where clearly appropriate, or diagrams drawn are entirely unlabelled, misleading, or irrelevant to the specific sub-part asked
Examples & nomenclature	20%	10	Uses precise nomenclature throughout: E-cadherin/N-cadherin, α/β/γ-catenin in (a); actin, tubulin, keratin, vimentin, desmin in (b); specific codon examples (AUG start, UGG tryptophan), Crick's wobble rules in (c); recombination nodules, synaptonemal complex in (d); Pearson's r, Spearman's rho in (e)	Uses generic terms without specific protein/gene names: 'cell adhesion proteins' without cadherin specificity in (a), 'protein fibers' without naming actin/tubulin in (b), 'start codon' without AUG in (c), 'exchange of parts' without chiasma terminology in (d), 'relationship between variables' without coefficient naming in (e)	Uses incorrect or invented terminology, or provides no specific examples where the sub-part clearly demands named entities; confuses homologous with homologous recombination mechanisms
Process explanation	25%	12.5	Captures dynamic mechanisms concisely: homophilic binding and catenin linkage to actin in (a), treadmilling/ dynamic instability in microtubules in (b), ribosomal A/P/E site codon-anticodon verification in (c), strand invasion and resolution via Holliday junction in (d), covariance calculation and significance testing in (e)	Describes static structures without explaining how processes operate: states adhesion molecules exist without binding mechanism in (a), lists cytoskeletal functions without explaining how they generate force in (b), states genetic code is triplet without explaining reading frame maintenance in (c), mentions exchange without synaptonemal complex role in (d), defines correlation without computational basis in (e)	Describes entirely wrong processes or provides no process explanation where central to the sub-part; confuses meiosis I and II events in crossing over description
Application / ecology	15%	7.5	Connects to applied significance: cancer metastasis and E-cadherin loss in (a), drug targets (taxol, cytochalasin) and crop improvement in (b), site-directed mutagenesis and synthetic biology in (c), mapping disease resistance genes in Indian crop varieties and hybrid vigor in (d), selection indices in rice/wheat breeding programs in (e)	Mentions generic significance without specific applications: 'important for development' in (a), 'helps cells move' in (b), 'needed for protein synthesis' in (c), 'creates variation' in (d), 'shows relationship' in (e); no Indian agricultural or biotechnological context	Omits significance entirely or provides irrelevant applications; discusses ecological succession when asked about cell adhesion, or describes food chains when asked about correlation

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