1. Which enzyme synthesizes the RNA primer required for DNA replication?

  • A. DNA polymerase III
  • B. DNA ligase
  • C. Primase
  • D. Helicase

Answer: C. Primase

Explanation: Primase synthesizes short RNA primers that provide the free 3′-OH group required for DNA polymerase to initiate DNA synthesis.

2. Which of the following is the largest lymphoid organ in the human body?

  • A. Thymus
  • B. Spleen
  • C. Tonsil
  • D. Bone marrow

Answer: B. Spleen

Explanation: The spleen is the largest lymphoid organ and filters blood, removes aged erythrocytes, and initiates immune responses.

3. Which hormone stimulates the secretion of thyroid hormones (T₃ and T₄)?

  • A. ACTH
  • B. FSH
  • C. TSH
  • D. LH

Answer: C. TSH

Explanation: Thyroid-stimulating hormone (TSH), secreted by the anterior pituitary, stimulates the thyroid gland to produce T₃ and T₄.

4. The anticodon is present on which type of RNA?

  • A. mRNA
  • B. rRNA
  • C. tRNA
  • D. hnRNA

Answer: C. tRNA

Explanation: The anticodon is a three-nucleotide sequence on tRNA that pairs with the complementary codon on mRNA during protein synthesis.

5. Which part of the human brain regulates body temperature, hunger, and thirst?

  • A. Cerebellum
  • B. Medulla oblongata
  • C. Hypothalamus
  • D. Pons

Answer: C. Hypothalamus

Explanation: The hypothalamus maintains homeostasis by regulating body temperature, appetite, thirst, and endocrine functions.

6. Which blood cells are primarily responsible for antibody production?

  • A. Neutrophils
  • B. B-lymphocytes
  • C. Eosinophils
  • D. Platelets

Answer: B. B-lymphocytes

Explanation: B-lymphocytes differentiate into plasma cells, which produce antibodies as part of humoral immunity.

7. Which scientist discovered the double-helical structure of DNA?

  • A. Meselson and Stahl
  • B. Jacob and Monod
  • C. Watson and Crick
  • D. Griffith

Answer: C. Watson and Crick

Explanation: James Watson and Francis Crick proposed the double-helical model of DNA in 1953 based on X-ray diffraction data.

8. Which ecological pyramid is always upright?

  • A. Pyramid of numbers
  • B. Pyramid of biomass
  • C. Pyramid of energy
  • D. All of the above

Answer: C. Pyramid of energy

Explanation: Energy decreases at each successive trophic level according to the second law of thermodynamics; therefore, the pyramid of energy is always upright.

9. Which disease is caused by the Human Immunodeficiency Virus (HIV)?

  • A. Hepatitis
  • B. Tuberculosis
  • C. AIDS
  • D. Typhoid

Answer: C. AIDS

Explanation: HIV attacks helper T-lymphocytes (CD4⁺ cells), leading to Acquired Immunodeficiency Syndrome (AIDS).

10. Which plant growth regulator is primarily responsible for apical dominance?

  • A. Cytokinin
  • B. Gibberellin
  • C. Auxin (IAA)
  • D. Ethylene

Answer: C. Auxin (IAA)

Explanation: Auxin produced in the apical bud suppresses the growth of lateral buds, resulting in apical dominance.