UPHESC Assistant Professor Zoology 2025 PYQs

Concept: A monophyletic group (clade) = a common ancestor + ALL its descendants.

1. Paraphyletic: ancestor + some descendants (e.g. traditional "Reptilia" without birds).
2. Polyphyletic: species from different ancestors grouped by convergent traits (e.g. "warm-blooded animals"), i.e. scattered on the tree.

Short trick: Mono = one cut of the tree – snip one branch and take everything on it.

Concept: Splicing removes introns from pre-mRNA in the eukaryotic nucleus using the spliceosome (snRNPs).

1. Prokaryotic protein-coding genes generally have no introns (A).
2. There is no nucleus, so ribosomes start translating the mRNA while it is still being transcribed – no time window for processing (B).
3. Bacteria have no spliceosome/snRNPs (C).
4. All three together explain the absence of mRNA splicing.

Short trick: No intron, no nucleus, no spliceosome → no splicing.

Concept: H1 is the linker histone; it binds the linker DNA (~20–80 bp) where DNA enters and leaves the nucleosome.

1. Nucleosome + H1 = chromatosome (~166 bp).
2. H1 helps compact the 10 nm "beads-on-string" fibre into the 30 nm fibre.
3. H2A, H2B, H3 (and H4) form the core octamer.

Short trick: H-ONE = the ONE outside the core.

Concept: Cladistics (phylogenetic systematics, Willi Hennig 1950) groups organisms by shared derived characters (synapomorphies) reflecting common ancestry; output = cladogram.

1. Phenetics/numerical taxonomy (Sokal & Sneath) uses overall similarity of many characters, not ancestry.
2. Morphological taxonomy uses form alone.

Short trick: Clade = branch of the family tree → evolutionary.

Concept: Renal glucosuria is glucose in urine despite normal blood glucose, due to a defect in tubular reabsorption (low renal threshold; e.g. SGLT2/SLC5A2 mutation).

1. Normally glucose spills into urine only above the renal threshold (~180 mg/dL), as in diabetes mellitus (option A).
2. In renal glucosuria the threshold is lowered, so urine sugar appears at normal plasma glucose.

Short trick: "Renal" = fault in the kidney, not in the blood → normal blood sugar.

Concept: Many anaerobic excavates have lost typical mitochondria and keep only reduced organelles.

1. a – true: diplomonads (Giardia) lack mitochondria; they have tiny mitosomes.
2. b – false: retortamonads also lack mitochondria.
3. c – false: parabasalids (Trichomonas) have hydrogenosomes, not true mitochondria.
4. d – true: Euglena (Euglenozoa) has normal mitochondria with discoid cristae.

Short trick: Giardia → mitosome; Trichomonas → hydrogenosome; Euglena → real mitochondria.

Concept: LAP2 (lamina-associated polypeptide 2, a LEM-domain protein) binds lamins and chromatin (via BAF) and is a key regulator of lamin organisation and nuclear-envelope assembly.

1. LAP2β (inner nuclear membrane) anchors lamin B; nucleoplasmic LAP2α binds and regulates lamin A/C.
2. Calmodulin and lipids are not lamin regulators; kinases (CDK1) only act transiently at mitosis by phosphorylation.

Short trick: LAP = Lamina-Associated Polypeptide → regulates lamins.

Concept: Mendel derived the law of independent assortment from the dihybrid cross (round-yellow × wrinkled-green), whose F₂ gave 9 : 3 : 3 : 1.

1. 9:3:3:1 = (3:1) × (3:1), showing the two gene pairs segregate independently.
2. 3 : 1 – monohybrid phenotypic ratio (law of segregation/dominance); 1 : 2 : 1 – monohybrid genotypic ratio.
3. 1 : 1 : 1 : 1 is the dihybrid test-cross ratio, which confirms it, but the classical ratio is 9:3:3:1.

Short trick: Two genes → (3+1)² = 16 → 9:3:3:1.

Concept: Adaptive radiation = rapid diversification of one ancestral stock into many forms filling different niches (H. F. Osborn).

1. Darwin's finches of the Galápagos – beaks adapted to seeds, insects, cactus.
2. Mammals – after dinosaur extinction, radiated into runners, fliers (bats), swimmers (whales), burrowers; Australian marsupials.
3. Birds – diverse beaks, feet and wings for many habitats.

Short trick: One ancestor → many niches = radiation; all three groups show it.

Concept: Bicoid is the maternal-effect morphogen that specifies the anterior (head/thorax) of the Drosophila embryo.

1. bicoid mRNA is localised at the anterior pole; its protein forms an anterior-to-posterior gradient and activates hunchback.
2. Nanos – posterior maternal determinant.
3. Engrailed – segment-polarity gene; Knirps (printed "Krirps") – gap gene.

Short trick: Bicoid = Brain end (anterior); Nanos = Nether end (posterior).

Concept: In deuterostomes the blastopore becomes the anus and the mouth forms second; cleavage is radial and indeterminate, coelom enterocoelous.

1. Deuterostomes: Echinodermata (starfish, sea urchin), Hemichordata, Chordata.
2. Arthropods, molluscs and annelids are protostomes (blastopore → mouth, spiral determinate cleavage, schizocoelous).

Short trick: "Deutero = second mouth": Echinoderms + Chordates (E-C).

Concept: Integral membrane proteins have hydrophobic α-helical (or β-barrel) segments that sit among the fatty-acid tails of the bilayer.

1. Hydrophobic interactions between these non-polar amino-acid side chains and lipid tails hold proteins in the membrane (Singer & Nicolson, 1972).
2. That is why detergents are needed to extract integral proteins.
3. Ionic/hydrophilic interactions hold only peripheral proteins; covalent lipid anchors are a minor case.

Short trick: Water-hating protein part hides in the water-hating lipid core.

Concept: Calsequestrin is a high-capacity, low-affinity Ca²⁺-binding protein inside the sarcoplasmic reticulum (terminal cisternae) of muscle.

1. Each molecule binds ~40–50 Ca²⁺, storing calcium for release through ryanodine receptors.
2. Calmodulin and troponin C are cytosolic Ca-binding proteins; titin is an elastic sarcomere protein.

Short trick: Cal-sequester-in = sequesters (stores) calcium inside SR.

Concept: The respiratory rhythm centre (dorsal and ventral respiratory groups, pre-Bötzinger complex) lies in the medulla oblongata.

1. Pons has the pneumotaxic and apneustic centres, which only modify (fine-tune) the medullary rhythm.
2. Medullary central chemoreceptors also sense CO₂/H⁺.
3. Cerebellum – posture/coordination; hypothalamus – temperature, hunger etc.

Short trick: Medulla = "vital centres" – breathing, heartbeat, BP.

Concept: A ligand (Latin ligare, to bind) is the signalling molecule – hormone, neurotransmitter, growth factor – that binds specifically to a receptor.

1. Receptor – the protein that receives the ligand.
2. Effector – downstream enzyme/channel activated (e.g. adenylyl cyclase).
3. "Epitome" is not a signalling term (epitope is the antigenic site for an antibody).

Short trick: Ligand → Receptor → Transducer → Effector → Response.

Concept: In freeze-fracture, a frozen cell is split; the fracture plane runs through the hydrophobic middle of the bilayer, separating the two leaflets.

1. A metal (platinum-carbon) replica of the exposed P-face and E-face is viewed in the EM.
2. Integral membrane proteins appear as intramembrane particles – strong evidence for the fluid mosaic model.
3. Light-microscope methods (phase-contrast, bright field, multiphoton) cannot resolve the inside of a 7–8 nm membrane.

Short trick: Freeze → crack the bilayer → see inside (P-face/E-face).

Concept: Link each respiratory component with its role.

1. Molecular O₂ is the final acceptor of electrons + H⁺, forming water → hydrogen acceptor (II).
2. Cytochrome c is a mobile electron carrier/acceptor between complex III and IV (III).
3. Pyruvate dehydrogenase converts pyruvate → acetyl-CoA (IV).
4. ATP synthase (F_oF₁) is driven by the proton gradient and is reversible as a proton pump (I).

Short trick: PDH → Acetyl-CoA is the sure pair; only option A has c–IV.

Concept: Bacteria have homologues of all three eukaryotic cytoskeletal proteins.

1. FtsZ – tubulin homologue (GTPase); forms the Z-ring at the division site.
2. MreB – actin homologue (ATPase); maintains rod shape.
3. Crescentin – intermediate-filament homologue (Caulobacter).
4. MotA/MotB and PomA/PomB are flagellar motor stator proteins.

Short trick: FtsZ → Z-ring division (tubulin, like spindle); MreB → Body shape (actin).

Concept: Intrinsic bioremediation (natural attenuation) = degradation of pollutants by the indigenous (naturally occurring) microbes without human intervention.

1. Engineered/enhanced bioremediation adds nutrients, oxygen (biostimulation) or microbes (bioaugmentation).
2. In-situ/ex-situ only tell where treatment occurs (at the site vs after removal), not who does it.

Short trick: Intrinsic = "in-built" microbes, nothing added.

Concept: Complementation: two recessive mutants with the same phenotype, when crossed, give wild-type progeny if the mutations lie in different genes.

1. aaBB × AAbb → AaBb: each parent supplies the functional allele the other lacks.
2. Example: two deaf parents with mutations in different genes having children with normal hearing.
3. No wild type → mutations are alleles of the same gene (cis–trans test, Benzer).

Short trick: Complement = "fill each other's gap".