1. In eukaryotes, RNA processing includes all of the following except:

  • A. 5′ capping
  • B. Polyadenylation
  • C. Removal of introns
  • D. DNA replication

Answer: D. DNA replication

Explanation: Eukaryotic mRNA processing involves 5′ capping, 3′ poly-A tail addition, and splicing of introns. DNA replication is a separate process.

2. Which part of the nephron is impermeable to water but actively transports sodium and chloride ions?

  • A. Proximal convoluted tubule
  • B. Descending limb of Henle
  • C. Ascending limb of Henle
  • D. Collecting duct

Answer: C. Ascending limb of Henle

Explanation: The ascending limb is impermeable to water but actively reabsorbs Na⁺ and Cl⁻, helping establish the medullary osmotic gradient.

3. Which hormone stimulates the release of ovum from the Graafian follicle?

  • A. Follicle-stimulating hormone (FSH)
  • B. Luteinizing hormone (LH)
  • C. Estrogen
  • D. Progesterone

Answer: B. Luteinizing hormone (LH)

Explanation: A surge in LH triggers ovulation, leading to the release of the secondary oocyte from the Graafian follicle.

4. Which scientist proposed the wobble hypothesis explaining degeneracy of the genetic code?

  • A. Har Gobind Khorana
  • B. Francis Crick
  • C. Marshall Nirenberg
  • D. Jacob Monod

Answer: B. Francis Crick

Explanation: Francis Crick proposed the wobble hypothesis, explaining that flexibility in the third codon position allows one tRNA to recognize multiple codons.

5. Which leukocyte is most abundant in normal human blood?

  • A. Eosinophils
  • B. Basophils
  • C. Monocytes
  • D. Neutrophils

Answer: D. Neutrophils

Explanation: Neutrophils constitute about 60–65% of total white blood cells and serve as the first line of defence against bacterial infections.

6. Which scientist proposed the five-kingdom classification of living organisms?

  • A. Carolus Linnaeus
  • B. R.H. Whittaker
  • C. Ernst Haeckel
  • D. Carl Woese

Answer: B. R.H. Whittaker

Explanation: R.H. Whittaker proposed the five-kingdom system in 1969 based on cell structure, nutrition, and organization.

7. Which phase of meiosis is characterized by crossing over between homologous chromosomes?

  • A. Leptotene
  • B. Zygotene
  • C. Pachytene
  • D. Diplotene

Answer: C. Pachytene

Explanation: Crossing over occurs during the pachytene stage of Prophase I when homologous chromosomes are fully paired.

8. Which nitrogen-fixing bacterium forms symbiotic associations with leguminous plants?

  • A. Azotobacter
  • B. Rhizobium
  • C. Nitrosomonas
  • D. Clostridium

Answer: B. Rhizobium

Explanation: Rhizobium lives in root nodules of legumes and fixes atmospheric nitrogen into ammonia.

9. Which plant growth regulator is primarily responsible for breaking seed dormancy and promoting stem elongation?

  • A. Auxin
  • B. Ethylene
  • C. Gibberellin
  • D. Abscisic acid

Answer: C. Gibberellin

Explanation: Gibberellins promote stem elongation, seed germination, flowering in some plants, and break seed dormancy.

10. Which vitamin acts as a major fat-soluble antioxidant protecting cell membranes from oxidative damage?

  • A. Vitamin A
  • B. Vitamin D
  • C. Vitamin E
  • D. Vitamin K

Answer: C. Vitamin E

Explanation: Vitamin E (tocopherol) is a fat-soluble antioxidant that protects membrane lipids from free radical damage.