1. In the lac operon of Escherichia coli, the inducer molecule is:

  • A. Glucose
  • B. Lactose (allolactose)
  • C. Galactose
  • D. Maltose

Answer: B. Lactose (allolactose)

Explanation: Allolactose, derived from lactose, binds to the repressor protein and allows transcription of the lac operon.

2. Which blood vessel supplies oxygenated blood directly to the heart muscle?

  • A. Pulmonary artery
  • B. Coronary artery
  • C. Superior vena cava
  • D. Pulmonary vein

Answer: B. Coronary artery

Explanation: Coronary arteries arise from the aorta and supply oxygenated blood to the myocardium.

3. Which hormone increases blood calcium levels by stimulating bone resorption?

  • A. Calcitonin
  • B. Insulin
  • C. Parathyroid hormone (PTH)
  • D. Thyroxine

Answer: C. Parathyroid hormone (PTH)

Explanation: PTH raises blood calcium by stimulating bone resorption, increasing renal calcium reabsorption, and activating vitamin D.

4. Which enzyme catalyses the synthesis of RNA during transcription?

  • A. DNA polymerase
  • B. RNA polymerase
  • C. Reverse transcriptase
  • D. DNA ligase

Answer: B. RNA polymerase

Explanation: RNA polymerase synthesizes RNA using one strand of DNA as the template during transcription.

5. Which blood cells are primarily responsible for transporting oxygen in the human body?

  • A. Leukocytes
  • B. Platelets
  • C. Erythrocytes
  • D. Lymphocytes

Answer: C. Erythrocytes

Explanation: Red blood cells contain haemoglobin, which binds oxygen in the lungs and transports it to body tissues.

6. Which scientist discovered the phenomenon of transformation in bacteria?

  • A. Frederick Griffith
  • B. Alfred Hershey
  • C. Martha Chase
  • D. Oswald Avery

Answer: A. Frederick Griffith

Explanation: Griffith demonstrated bacterial transformation in 1928 while studying Streptococcus pneumoniae.

7. Which of the following is a greenhouse gas responsible for global warming?

  • A. Nitrogen
  • B. Oxygen
  • C. Carbon dioxide
  • D. Argon

Answer: C. Carbon dioxide

Explanation: Carbon dioxide traps heat in the atmosphere and is one of the major greenhouse gases contributing to climate change.

8. Double fertilization is a characteristic feature of:

  • A. Gymnosperms
  • B. Angiosperms
  • C. Bryophytes
  • D. Pteridophytes

Answer: B. Angiosperms

Explanation: In angiosperms, one male gamete fuses with the egg to form the zygote, while the other fuses with polar nuclei to form the endosperm.

9. The functional unit of the kidney is:

  • A. Alveolus
  • B. Neuron
  • C. Nephron
  • D. Glomerulus

Answer: C. Nephron

Explanation: The nephron is the structural and functional unit of the kidney responsible for urine formation.

10. Which vitamin deficiency causes pernicious anaemia?

  • A. Vitamin B₁
  • B. Vitamin B₂
  • C. Vitamin B₁₂
  • D. Vitamin C

Answer: C. Vitamin B₁₂

Explanation: Vitamin B₁₂ deficiency impairs red blood cell maturation and can lead to pernicious (megaloblastic) anaemia.