Agriculture 2023 Paper II 50 marks Explain

Q2

(a) Enlist the molecular models of cell membrane and explain the models given by S.J. Singer and G. Nicholson (1972), Green and Capaldi (1974) and Racker (1976). 20 (b) Give an account of seven different pairs of contrasting characters whose inheritance was studied by Mendel in Garden Pea (Pisum sativum). Give the reasons for Mendel's success in the study. 20 (c) Explain various theories of inheritance. Write down the evidences suggesting the presence of cytoplasmic inheritance in the crosses' results. 10

हिंदी में प्रश्न पढ़ें

(a) कोशिका झिल्ली के आणविक मॉडल को सूचीबद्ध कीजिए । एस.जे. सिंगर तथा जी. निकोल्सन (1972), ग्रीन तथा कैपाल्डी (1974) एवं रैकर (1976) के मॉडलों की व्याख्या कीजिए । 20 (b) विपरीत लक्षणों वाले सात विभिन्न जोड़ों का विवरण दीजिए जिनकी वंशागति का अध्ययन गार्डन मटर (पाइसम सेटाइवम) में मेंडल द्वारा किया गया था । इस अध्ययन में मेंडल की सफलता के कारण दीजिए । 20 (c) वंशागति के विभिन्न सिद्धांतों की व्याख्या कीजिए । क्रॉसों के परिणामों में कोशिकाद्रव्यी वंशागति की उपस्थिति का संकेत देने वाले प्रमाणों को लिखिए । 10

Evaluate your answer to this question → See all 2023 Agriculture questions

Directive word: Explain

This question asks you to explain. 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 'explain' demands clear exposition with causal reasoning across all three parts. Allocate approximately 40% of word budget to part (a) given its 20 marks and technical complexity, 35% to part (b) for Mendelian genetics, and 25% to part (c) for inheritance theories. Structure: brief introduction noting the evolution from structural to functional membrane biology and classical to modern genetics; systematic treatment of each sub-part with sub-headings; conclusion synthesizing how membrane fluidity and cytoplasmic inheritance challenged the nuclear-centric Mendelian framework.

Key points expected

  • Part (a): Enlists at least 5 membrane models (Gorter-Grendel, Danielli-Davson, Robertson unit membrane, fluid mosaic, lipid-globular protein mosaic) with correct chronology; explains Singer-Nicholson fluid mosaic model (integral vs peripheral proteins, lipid bilayer fluidity, asymmetry); Green-Capaldi model (lipid-globular protein mosaic with repeating units); Racker model (complex mosaic with specific lipid-protein associations and transport functions)
  • Part (b): Lists all seven Mendelian character pairs with correct dominant/recessive relationships (stem height, flower position, pod shape, pod color, seed shape, seed color, flower color); explains reasons for success (choice of Pisum sativum with true-breeding lines, controlled selfing/crossing, use of mathematical analysis, study of single characters, large sample sizes, selection of discrete traits)
  • Part (c): Explains preformationism, pangenesis, germ plasm theory, and modern synthetic theory; describes cytoplasmic inheritance with evidence from reciprocal crosses (plastid inheritance in Mirabilis jalapa/4-o'clock plant variegation, CO2 sensitivity in Drosophila with sigma virus, mitochondrial inheritance in yeast petite mutants, male sterility in maize/Indian sorghum)
  • Demonstrates understanding of how membrane models progressed from static to dynamic conceptions, and how Mendelian principles were later modified by cytoplasmic inheritance discoveries
  • Connects cytoplasmic inheritance to practical applications in hybrid seed production (CMS lines in Indian agriculture) and membrane biology to abiotic stress tolerance mechanisms

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Precise terminology for all three models in (a) with correct dates and distinguishing features; accurate 7 Mendelian traits with proper dominance relationships; comprehensive coverage of inheritance theories with correct attribution; specific molecular mechanisms for cytoplasmic inheritance evidenceMostly correct identification of models and traits with minor errors in dates or dominance relationships; basic coverage of inheritance theories but confused attribution; generic description of cytoplasmic inheritance without specific molecular evidenceConfusion between models (e.g., calling Singer-Nicholson a unit membrane model); incorrect trait identification or dominance; missing major theories; inability to distinguish cytoplasmic from nuclear inheritance
Quantitative reasoning15%7.5Cites Mendel's actual ratios (3:1, 9:3:3:1) with sample sizes; mentions statistical significance of results; quantitative aspects of membrane composition (protein-lipid ratios in different models); numerical data from cytoplasmic inheritance crossesMentions Mendelian ratios without specific numbers; general awareness that mathematical analysis was key to Mendel's success; qualitative rather than quantitative treatment of membrane compositionNo quantitative content; incorrect ratios; failure to recognize the mathematical foundation of Mendel's methodology
Indian context examples15%7.5Cites Indian research on cytoplasmic male sterility (CMS) in sorghum, pigeonpea, or rice (e.g., A1, A2, A3, A4 systems); mentions Indian work on membrane fluidity under heat stress; references to Indian geneticists like M.S. Swaminathan's contributions to understanding cytoplasmic inheritance in crop improvementGeneric mention of CMS in hybrid seed production without Indian specifics; passing reference to Indian agriculture applications without named examples or researchersNo Indian context; entirely foreign examples when Indian equivalents exist; failure to connect to Indian agricultural relevance
Diagram / process25%12.5Clear labeled diagrams for fluid mosaic model (showing integral proteins, cholesterol, carbohydrate chains), Green-Capaldi repeating units, and Racker's complex mosaic; Punnett squares or forked-line diagrams for Mendelian crosses; schematic of reciprocal cross showing maternal inheritance pattern; flowchart of membrane model evolutionBasic sketch of fluid mosaic model; simple monohybrid cross diagram; verbal description of reciprocal cross results without visual representationNo diagrams despite explicit need for visual representation; poorly labeled or incorrect diagrams; diagrams that contradict textual explanation
Policy / extension angle20%10Explicitly connects cytoplasmic male sterility to India's hybrid seed programme and food security; discusses membrane biology applications in developing stress-tolerant crop varieties under climate change; mentions biosafety considerations in cytoplasmic gene transfer; links Mendelian principles to Plant Variety Protection and Farmers' Rights ActBrief mention of hybrid seed technology or stress tolerance without policy depth; generic statement about importance of genetics for agricultureNo extension or policy relevance; purely academic treatment without application to Indian agricultural development; misses opportunity to discuss practical breeding implications

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 Agriculture 2023 Paper II