All 8 questions from UPSC Civil Services Mains Zoology 2022 Paper II (400 marks total). Every stem reproduced in full, with directive-word analysis, marks, word limits, and answer-approach pointers.
8Questions
400Total marks
2022Year
Paper IIPaper
Topics covered
Cell biology, genetics and evolution (1)Cell organelles and membrane transport (1)Molecular biology and genetic engineering (1)Evolution and biodiversity (1)Immunology, physiology and development (1)Biochemistry and molecular biology (1)Physiology and sensory systems (1)Developmental biology and reproduction (1)
A
Q1
50M150wCompulsorydrawCell biology, genetics and evolution
Write your answer in about 150 words for each of the following : 10×5=50
(a) Draw the structure of a microtubule and explain its role in chromosomal movements during cell division.
(b) What is mutation? Write a brief note on various types of point mutations.
(c) Give schematic organization of cosmid. Why is it preferred over plasmid for gene cloning?
(d) Explain Hardy-Weinberg law of equilibrium and mention the factors that upset the equilibrium.
(e) Write a note on the theory of natural selection.
हिंदी में पढ़ें
निम्नलिखित प्रत्येक के लिए लगभग 150 शब्दों में अपना उत्तर लिखिए : 10×5=50
(a) एक सूक्ष्म-नलिका की संरचना बनाइए तथा कोशिका विभाजन के दौरान गुणसूत्रों के संचलन में इसकी भूमिका की व्याख्या कीजिए।
(b) उत्परिवर्तन क्या है? विभिन्न प्रकार के बिंदु उत्परिवर्तनों पर एक संक्षिप्त टिप्पणी लिखिए।
(c) कॉस्मिड का व्यवस्थित संगठन प्रस्तुत कीजिए। जीन क्लोनिंग के लिए प्लाज्मिड के ऊपर इसको वरियता क्यों दी जाती है?
(d) हार्डी-विनबर्ग के साम्यावस्था के नियम की व्याख्या कीजिए तथा उन कारकों का उल्लेख कीजिए जो साम्यावस्था को अनियमित करते हैं।
(e) प्राकृतिक चयन के सिद्धांत पर एक टिप्पणी लिखिए।
Answer approach & key points
Framework: Zoology, Paper 2. (a) explain: definition/context > points in order > small example > short close | (b) define: precise definition > the distinguishing feature > one example | (c) describe: define > structure or process in order > labelled diagram > significance | (d) explain: definition/context > points in order > small example > short close | (e) write short notes: define > 3-4 key features > one example > one-line significance Full marks: All five parts within about 150 words: labelled microtubule and cosmid diagrams, point mutations with effects and an example, Hardy-Weinberg equation with its factors, and natural selection with postulates and an example.
Labelled structure: hollow cylinder (about 25 nm) of 13 protofilaments of α/β-tubulin heterodimers, with plus (β) and minus (α) ends
Kinetochore microtubules capture and align chromosomes and pull chromatids poleward in anaphase A by depolymerisation
Polar and astral microtubules with motors (kinesin, dynein) separate the poles in anaphase B
Mutation as a sudden heritable change in the base sequence; point mutation as change of a single base pair
Substitutions: transitions (purine↔purine, pyrimidine↔pyrimidine) and transversions (purine↔pyrimidine)
Effects: silent, missense (with an example such as sickle-cell GAG→GTG, Glu→Val) and nonsense; frameshift by insertion or deletion
Labelled schematic: plasmid ori, selectable marker (for example ampᴿ), λ cos site and cloning site
Cosmid as plasmid plus λ cos site: packaged in vitro into λ heads, introduced by infection, replicates as a plasmid
Preference: inserts of about 35–45 kb against about 10 kb or less in a plasmid, so fewer clones for a genomic library
Law: allele and genotype frequencies stay constant in a large, randomly mating population without mutation, migration, selection or drift
p + q = 1 and p² + 2pq + q² = 1, with the derivation that p′ = p
(a) What is rough endoplasmic reticulum (RER)? Describe in detail the various modifications of secretory proteins occurring in the lumen of RER. 20
(b) Define endomitosis. Describe in detail the structure of a polytene chromosome highlighting the importance of puffs. 15
(c) What is facilitated diffusion? Describe the mechanism of active transport across the plasma membrane with suitable example. 15
हिंदी में पढ़ें
(a) खुरदरी अंतर्द्रव्यी जालिका (आर० ई० आर०) क्या है? आर० ई० आर० की अवकाशिका में होने वाले स्रावी प्रोटीनों के विभिन्न परिवर्तनों का विस्तृत वर्णन कीजिए। 20
(b) अंतःसूत्रण की परिभाषा लिखिए। आफुल्ल (पफ) के महत्व को दर्शाते हुए बहुपट्टीय गुणसूत्र की संरचना का विस्तृत वर्णन कीजिए। 15
(c) सुकृत विसरण क्या है? प्रद्रव्य झिल्ली के आर-पार सक्रिय अभिगमन की प्रक्रिया का उपयुक्त उदाहरण के साथ वर्णन कीजिए। 15
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) describe: define > structure or process in order > labelled diagram > significance | (b) describe: define > structure or process in order > labelled diagram > significance | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: All three parts correct: signal-sequence entry, glycosylation, folding, disulphide bonding and quality control in the RER lumen; endomitosis with polytene structure and the importance of puffs; facilitated diffusion with the Na⁺–K⁺ ATPase mechanism.
RER defined as ribosome-studded cisternae continuous with the nuclear envelope; entry of the chain by signal sequence, SRP and translocon
N-linked glycosylation (oligosaccharide transferred from dolichol to Asn-X-Ser/Thr) and cleavage of the signal peptide
Folding and quality control: BiP, calnexin/calreticulin, disulphide bonds by PDI, degradation of misfolded proteins (ERAD)
Endomitosis as chromosome duplication within an intact nuclear envelope without nuclear or cell division, giving polyploidy; polytene chromosomes by endoreduplication
Structure: up to 1,024 chromatids in register, somatic pairing, chromocenter, bands and interbands
Puffs as uncoiled bands of active transcription (Balbiani rings), and their importance: differential gene activity, ecdysone and heat-shock response
Facilitated diffusion: passive, down the gradient, through specific carriers or channels, saturable, no ATP
Active transport: against the gradient with energy; primary (ATP-driven) and secondary (ion-gradient-driven)
Na⁺–K⁺ ATPase cycle: phosphorylation and conformational change, 3 Na⁺ out and 2 K⁺ in per ATP
50MillustrateMolecular biology and genetic engineering
(a) Sketch out a basic transcription unit and illustrate the RNA polymerase II associated assembly of a transcription initiation complex during expression of a eukaryotic gene. 20
(b) Illustrate the steps of constructing a recombinant c-DNA from an m-RNA. 15
(c) Explain the following :
(i) Stepwise intrinsic mechanism of apoptotic induction
(ii) Principle of DNA fingerprinting 15
हिंदी में पढ़ें
(a) एक आधारभूत अनुलेखन इकाई का रेखाचित्र बनाइए तथा एक सुकेंद्रकीय जीन की अभिव्यक्ति के दौरान आर० एन० ए० पॉलिमरेज II से संबंधित अनुलेखन प्रारंभ सम्मिश्र का सचित्र विवरण दीजिए। 20
(b) एक m-आर० एन० ए० से एक पुनर्योगज c-डी० एन० ए० बनाने के क्रमों को सचित्र समझाइए। 15
(c) निम्नलिखित की व्याख्या कीजिए :
(i) एपोप्टोटिक प्रेरण की चरणबद्ध आंतरिक क्रियाविधि
(ii) डी० एन० ए० फिंगरप्रिंटिंग का सिद्धांत 15
Answer approach & key points
Framework: null. (a) describe: define > structure or process in order > labelled diagram > significance | (b) trace: start point > the stages in sequence > end point > what changed | (c) explain: definition/context > points in order > small example > short close Full marks: All parts complete and in order: labelled transcription unit with TFIID-to-TFIIH assembly and CTD phosphorylation, the steps of cDNA cloning, the cytochrome c–apoptosome–caspase cascade, and the VNTR/STR principle with its procedure.
Labelled transcription unit: enhancer, promoter (CAAT box, TATA box, Inr), start site +1, exons and introns, polyadenylation signal and termination region
Ordered assembly: TFIID (TBP at the TATA box), TFIIA, TFIIB, RNA polymerase II with TFIIF, TFIIE, TFIIH
TFIIH helicase melting the DNA (open complex) and CDK7 phosphorylation of the CTD (Ser5) for promoter escape
Isolation of poly(A)⁺ mRNA and first-strand synthesis with an oligo(dT) primer and reverse transcriptase
Second-strand synthesis (RNase H with DNA polymerase I, or hairpin priming and S1 nuclease) giving double-stranded cDNA
Ligation into a vector through linkers or adaptors and cohesive ends; transformation, selection and screening to obtain the cDNA clone or library
Intrinsic pathway: BH3-only proteins, Bax and Bak, mitochondrial outer membrane permeabilisation and release of cytochrome c
Apaf-1 apoptosome, caspase-9 and executioner caspases-3, -6 and -7, leading to DNA fragmentation
DNA fingerprinting: VNTR or STR polymorphism, restriction digestion or PCR, electrophoresis, Southern blot with probe, comparison of bands
(a) What is fossil? Describe the origin and evolution of horse based on the fossil records. 20
(b) Define variation. Describe different types of variations and their role in evolution. 15
(c) What is biodiversity? Describe the major types of biodiversities found in nature. 15
हिंदी में पढ़ें
(a) जीवाश्म क्या होता है? जीवाश्म प्रमाणों पर आधारित घोड़े के उद्भव एवं विकास का वर्णन कीजिए। 20
(b) विभिन्नता को परिभाषित कीजिए। विभिन्न प्रकार की विभिन्नताओं और विकास में उनकी भूमिका का वर्णन कीजिए। 15
(c) जैव-विविधता क्या है? प्रकृति में पायी जाने वाली जैव-विविधताओं के प्रमुख प्रकारों का वर्णन कीजिए। 15
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) describe: define > structure or process in order > labelled diagram > significance | (b) describe: define > structure or process in order > labelled diagram > significance | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: All three parts correct: fossil definition and the ordered horse lineage with its trends, the types and evolutionary role of variation, and genetic, species and ecosystem diversity with examples.
Definition of fossil with the modes of preservation
Ordered stages with genera and ages: Eohippus, Mesohippus, Merychippus, Pliohippus or Dinohippus, Equus
Trends: toes reduced (four and three toes to a single hoof), limbs lengthened, size increased and tooth crowns raised, linked to the change from forest to grassland
Definition of variation
Types: somatic and germinal (heritable); continuous and discontinuous, with examples
Role: heritable variation as the raw material of natural selection, adaptation and speciation, with an example
Definition: variability within species, between species and of ecosystems
Genetic, species and ecosystem diversity, each explained
50M150wCompulsoryexplainImmunology, physiology and development
Write your answer in about 150 words for each of the following : 10×5=50
(a) Define immunity. Explain cell-mediated immune response in vertebrates with suitable diagram.
(b) Describe the structure and functions of mammalian placenta.
(c) Explain the functions of neutrophils, basophils and lymphocytes.
(d) Illustrate the counter-current mechanism by vasa recta and mention its physiological importance.
(e) Define biogenetic law. Write the characteristics of Haeckel's theory of recapitulation.
हिंदी में पढ़ें
निम्नलिखित प्रत्येक के लिए लगभग 150 शब्दों में अपना उत्तर लिखिए : 10×5=50
(a) प्रतिरक्षा को परिभाषित कीजिए। उपयुक्त आरेख के साथ कशेरुकियों में कोशिका-माध्यित प्रतिरक्षा अनुक्रिया की व्याख्या कीजिए।
(b) स्तनधारी अपरा की संरचना तथा कार्यों का वर्णन कीजिए।
(c) न्यूट्रोफिल, बेसोफिल तथा लिम्फोसाइट के कार्यों की व्याख्या कीजिए।
(d) वासा रेक्टा के प्रतिधारा तंत्र का सचित्र विवरण दीजिए, तथा उसके कार्यिकीय महत्व का उल्लेख कीजिए।
(e) बायोजेनेटिक नियम को परिभाषित कीजिए। पुनरावृत्ति के हैकल सिद्धांत की विशेषताएं लिखिए।
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) explain: definition/context > points in order > small example > short close | (b) describe: define > structure or process in order > labelled diagram > significance | (c) explain: definition/context > points in order > small example > short close | (d) explain: definition/context > points in order > small example > short close | (e) define: precise definition > the distinguishing feature > one example Full marks: Precise definitions, labelled diagrams, specific mechanisms, and named examples.
Definition of immunity: innate and adaptive resistance to pathogens and foreign or abnormal cells
Sequence: antigen presentation on MHC-II to CD4+ helper T cell, IL-2 and interferon-γ, CD8+ cytotoxic T cell killing by perforin and granzymes
Labelled diagram of the T-cell response
Structure: chorion and decidua basalis, chorionic villi in maternal blood spaces, placental barrier layers
Functions: exchange, endocrine (hCG, progesterone, oestrogens, hPL) and immunological
Neutrophils: chemotaxis, phagocytosis, respiratory burst or extracellular traps
Basophils: IgE-triggered degranulation releasing histamine, heparin and leukotrienes in allergy
Lymphocytes: B cells make antibodies; helper, cytotoxic and regulatory T cells; NK cells
Hairpin vasa recta beside the loop of Henle: water out and solutes in on the descending limb, the reverse on the ascending limb
Preservation of the medullary osmotic gradient (about 300 to 1200 mOsm/L) made by the loop of Henle
Importance: ADH-controlled water reabsorption and concentrated urine
(a) Draw the molecular structure of ATP synthase and diagrammatically explain the chemiosmotic concept of ATP synthesis. 20
(b) Illustrate the following :
(i) A = T and G ≡ C base pairing as a part of DNA double strand
(ii) Michaelis-Menten kinetic pattern of an enzymatic reaction 15
(c) Explain the cellular mechanism of action of steroid hormones. 15
हिंदी में पढ़ें
(a) ए० टी० पी० सिन्थेज की आण्विक संरचना का चित्र बनाइए तथा ए० टी० पी० संश्लेषण की रसोप्रसरणी (केमिऑस्मोटिक) संकल्पना को आरेखीय रूप से समझाइए। 20
(b) निम्नलिखित को सचित्र समझाइए :
(i) डी० एन० ए० द्वैलड़ी के एक भाग के रूप में A = T तथा G ≡ C का बेस युग्मन
(ii) एक प्रकिण्व की अभिक्रिया की माइकेलिस-मेंटेन गतिक प्राक्रता 15
(c) स्टेरॉयड हार्मोनों की क्रिया की कोशिकीय कार्यप्रणाली की व्याख्या कीजिए। 15
Answer approach & key points
Framework: null. (a) explain: definition/context > points in order > small example > short close | (b) describe: define > structure or process in order > labelled diagram > significance | (c) explain: definition/context > points in order > small example > short close Full marks: All parts fully answered with labelled diagrams, precise mechanisms, and specific examples
Chemiosmotic sequence: proton pumping by the electron transport chain, proton-motive force, H⁺ return through F₀ turning the rotor, ATP formed in F₁ (Mitchell)
Binding-change mechanism (open, loose, tight) converting ADP + Pi to ATP
(i) Antiparallel strands; purine–pyrimidine pairing with two hydrogen bonds for A=T and three for G≡C
(ii) Hyperbolic v against [S] curve with Vmax plateau and Km at Vmax/2, and the equation v = Vmax[S]/(Km + [S])
Lipid-soluble hormone crosses the membrane and binds an intracellular receptor (hsp90 released)
Dimerised complex binds the hormone response element and alters transcription through coactivators and RNA polymerase II
New mRNA and proteins give a slow, long-lasting response
(a) What are intestinal glands? Describe the roles of intestinal juices in digestion and absorption of food. 20
(b) Define thermoregulation. How do homeotherms regulate body temperature in hot and cold climates? 15
(c) Draw the structure of retina and explain the mechanism of vision in mammalian eye. 15
हिंदी में पढ़ें
(a) आंत्र प्रथियां क्या होती हैं? भोजन के पाचन तथा अवशोषण में आंत्र रसों की भूमिकाओं का वर्णन कीजिए। 20
(b) तापीय नियमन को परिभाषित कीजिए। गर्म एवं ठंडे वातावरण में समतापी अपने शरीर के ताप को कैसे नियंत्रित करते हैं? 15
(c) रेटिना की संरचना को चित्रित कीजिए तथा स्तनधारी आंख में दृश्यता की क्रियाविधि की व्याख्या कीजिए। 15
Answer approach & key points
Framework: UPSC Zoology Paper 2. (a) describe: define > structure or process in order > labelled diagram > significance | (b) explain: definition/context > points in order > small example > short close | (c) explain: definition/context > points in order > small example > short close Full marks: Precise definitions, detailed mechanisms, and accurate labelled diagrams.
Intestinal glands are the crypts of Lieberkühn in the small-intestinal mucosa; cell types; alkaline watery juice (about 1.8 L a day)
Digestion: enterokinase activating trypsinogen, brush-border disaccharidases and peptidases, nucleotidases
Absorption: watery vehicle, brush-border digestion coupled to uptake (SGLT1, GLUT5, GLUT2), fat absorption through chylomicrons and lacteals
Definition and hypothalamic negative-feedback control
Hot climate: vasodilation, sweating or panting, reduced heat production, behaviour
Cold climate: vasoconstriction, piloerection and insulation, shivering and non-shivering thermogenesis, counter-current exchange
Labelled retinal layers from pigment epithelium to nerve fibre layer, with rods, cones, bipolar and ganglion cells
Rod phototransduction: rhodopsin, 11-cis to all-trans retinal, transducin, phosphodiesterase, fall in cGMP, channel closure, hyperpolarisation
Transmission through bipolar and ganglion cells, optic nerve and visual cortex
(a) What is stem cell? Discuss the types of stem cells and their application in therapeutic uses in human. 20
(b) Explain the mechanism of spermatogenesis in mammals with suitable diagram. 15
(c) Describe the hormonal regulation of metamorphosis in amphibians. 15
हिंदी में पढ़ें
(a) मूल कोशिका क्या होती है? मूल कोशिकाओं के प्रकारों एवं मनुष्य के रोग निवारण में उनके अनुप्रयोग की व्याख्या कीजिए। 20
(b) उपयुक्त आरेख के साथ स्तनपायी में शुक्रजनन की प्रक्रिया की व्याख्या कीजिए। 15
(c) उभयचरों में कायांतरण के हार्मोनी नियमन का वर्णन कीजिए। 15
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) discuss: intro > 3-4 dimensions > example > balanced close | (b) explain: definition/context > points in order > small example > short close | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise definitions, labelled diagrams, specific taxon names, and clear mechanistic links.
Definition: self-renewal together with differentiation
Types by potency and source: totipotent, pluripotent (embryonic, induced), multipotent (adult), unipotent
Therapeutic uses: haematopoietic transplantation for blood disorders, with other applications and trials
Seminiferous tubule diagram: spermatogonia, primary and secondary spermatocytes, spermatids, spermatozoa, Sertoli and Leydig cells
Stages: multiplication, growth, maturation by meiosis I and II with correct ploidy (four sperm per primary spermatocyte)
Spermiogenesis changes: acrosome, condensed nucleus, middle piece and tail, residual body
Thyroid hormones (T₄, T₃) as the main inducers, under hypothalamic (CRH) and pituitary (TSH) control
Stage-wise changes: premetamorphosis, prometamorphosis and climax, with limb growth, tail resorption, gut and gill changes