UPHESC Assistant Professor Zoology 2025 PYQs

Concept: In humans the Y chromosome (SRY gene) determines maleness regardless of the number of X chromosomes.

1. XXY (47 chromosomes) = Klinefelter syndrome: phenotypic male, tall, small testes, sterile, sometimes gynaecomastia.
2. Super female is XXX; this differs from Drosophila, where the X:A ratio decides sex.

Short trick: "Y = guy" – any Y makes a male in humans.

Concept: Though worded as a sequence, this is a disease–pathogen matching.

1. Jaundice (Weil's disease, leptospirosis) – spirochaete Leptospira (I–b).
2. Kala-azar (visceral leishmaniasis) – Leishmania donovani, spread by sandfly (II–a).
3. Bacillary dysentery – Shigella (III–c).
4. Whooping cough – Bordetella pertussis (IV–d).

Short trick: Kala-azar ↔ Leishmania is the anchor; only option A has II–a with I–b.

Concept: Ribophorins I and II are transmembrane glycoproteins of the RER membrane that help bind the large (60S) ribosomal subunit; they are part of the oligosaccharyl-transferase complex.

1. Glycophorins – sialoglycoproteins of the RBC membrane.
2. Lipophorins – lipid-carrying proteins of insect haemolymph.
3. Transferrin – iron-transport protein of plasma.

Short trick: Ribo-phorin = "ribosome carrier" on RER.

Concept: Optimal foraging theory (MacArthur & Pianka, 1966) says natural selection favours foraging that maximises net energy gain per unit time, i.e. benefit minus cost.

1. Animals choose prey, patch and time spent so that search/handling energy cost is minimised relative to intake (e.g. Charnov's marginal value theorem).
2. B, C, D describe need, capacity or instinct – not optimisation.

Short trick: "Optimal" = best profit: max energy in, min energy out.

Concept: Palaeozoic periods: Cambrian → Ordovician → Silurian → Devonian → Carboniferous → Permian; then Mesozoic; Pliocene is a late Cenozoic epoch.

1. Cambrian (I) 541–485 Ma.
2. Carboniferous (III) 359–299 Ma.
3. Permian (II) 299–252 Ma.
4. Pliocene (IV) 5.3–2.6 Ma. Order: I, III, II, IV.

Short trick: "Camels Often Sit Down Carefully, Perhaps" – Cam, Ord, Sil, Dev, Carb, Perm.

Concept: A sugar is reducing if it has a free anomeric (aldehyde/ketone) carbon.

1. Sucrose: glucose α1→β2 fructose – both anomeric carbons are bonded → non-reducing.
2. Raffinose (galactose–glucose–fructose) contains the sucrose linkage → non-reducing.
3. Glucose and maltose have a free anomeric carbon → reducing, so A, B and D are wrong.

Short trick: "Sucrose family" (sucrose, raffinose, stachyose) and trehalose are non-reducing.

Concept: Sterols (e.g. cholesterol) are essential in eukaryotes: they regulate membrane fluidity and are precursors of steroid hormones, bile acids and vitamin D.

1. A is true.
2. R is also true: cholesterol/oxysterols act as signalling molecules in development – cholesterol is covalently attached to Hedgehog and sterols activate Smoothened, acting as a second messenger in Hedgehog signalling.
3. This signalling role is one of the reasons sterols are physiologically essential, so R explains A.

Short trick: Cholesterol = membrane + hormones + Hedgehog signal → "essential".

Concept: Glucose binds non-enzymatically to haemoglobin (glycation); the % of HbA1c reflects the average blood glucose of the previous 2–3 months (RBC life ~120 days).

1. Used to diagnose and monitor diabetes mellitus: normal <5.7 %, prediabetes 5.7–6.4 %, diabetes ≥6.5 %.
2. Anaemia/thalassaemia actually make HbA1c unreliable; it is not a heart-attack marker (troponin is).

Short trick: A1c = "Average glucose over 3 months".

Concept: Logistic (Verhulst–Pearl) growth: $\frac{dN}{dt}=rN\left(\frac{K-N}{K}\right)$ – a sigmoid (S-shaped) curve.

1. At low N growth is nearly exponential; as N approaches carrying capacity K, the growth rate falls to zero and the population stabilises.
2. Constant per-capita growth rate gives exponential (J-shaped), not logistic, growth.

Short trick: J = exponential (no limit); S = logistic (stops at K).

Concept: Natural selection is adaptive and cumulative; the bottleneck effect is a form of random genetic drift.

1. A is true – selection acting over many generations accumulates differences that lead to speciation (Darwin).
2. R is true – a drastic fall in population size (bottleneck, e.g. cheetah, northern elephant seal) cuts genetic variation and can decide the species' future survival.
3. But drift is random and different from selection, so R does not explain A.

Short trick: Selection = non-random; bottleneck = chance → both true, no cause–effect.

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).