1. Which enzyme removes RNA primers and replaces them with DNA nucleotides during DNA replication in prokaryotes?

  • A. DNA polymerase I
  • B. DNA polymerase III
  • C. DNA ligase
  • D. Topoisomerase

Answer: A. DNA polymerase I

Explanation: DNA polymerase I possesses 5'→3' exonuclease activity that removes RNA primers and fills the gaps with DNA nucleotides.

2. Which chamber of the human heart has the thickest muscular wall?

  • A. Right atrium
  • B. Left atrium
  • C. Right ventricle
  • D. Left ventricle

Answer: D. Left ventricle

Explanation: The left ventricle pumps oxygenated blood to the entire body through the aorta and therefore has the thickest myocardium.

3. Which hormone is secreted by the corpus luteum after ovulation?

  • A. Estrogen only
  • B. Progesterone
  • C. Follicle-stimulating hormone
  • D. Luteinizing hormone

Answer: B. Progesterone

Explanation: The corpus luteum secretes progesterone, which prepares and maintains the uterine endometrium for implantation.

4. The process by which mRNA is synthesized from a DNA template is called:

  • A. Translation
  • B. Replication
  • C. Transcription
  • D. Translocation

Answer: C. Transcription

Explanation: During transcription, RNA polymerase synthesizes an RNA molecule using one strand of DNA as the template.

5. Which vitamin is synthesized in the skin when exposed to ultraviolet (UV) rays?

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

Answer: C. Vitamin D

Explanation: UV-B radiation converts 7-dehydrocholesterol in the skin into vitamin D₃ (cholecalciferol).

6. Which scientist experimentally proved that DNA replication is semiconservative?

  • A. Hershey and Chase
  • B. Griffith
  • C. Meselson and Stahl
  • D. Avery and MacLeod

Answer: C. Meselson and Stahl

Explanation: Meselson and Stahl demonstrated semiconservative DNA replication using Escherichia coli grown in nitrogen isotopes (¹⁵N and ¹⁴N).

7. Which type of immunity is produced after vaccination?

  • A. Natural passive immunity
  • B. Artificial passive immunity
  • C. Natural active immunity
  • D. Artificial active immunity

Answer: D. Artificial active immunity

Explanation: Vaccination stimulates the body's immune system to produce antibodies and memory cells without causing the disease.

8. Which trophic level contains herbivores in a food chain?

  • A. First trophic level
  • B. Second trophic level
  • C. Third trophic level
  • D. Fourth trophic level

Answer: B. Second trophic level

Explanation: Herbivores are primary consumers that feed directly on producers and occupy the second trophic level.

9. Which plant tissue is primarily responsible for the transport of water and minerals?

  • A. Phloem
  • B. Collenchyma
  • C. Xylem
  • D. Parenchyma

Answer: C. Xylem

Explanation: Xylem conducts water and dissolved mineral salts from the roots to the aerial parts of the plant.

10. Which scientist is known as the "Father of Modern Taxonomy"?

  • A. Aristotle
  • B. Carolus Linnaeus
  • C. Charles Darwin
  • D. Ernst Haeckel

Answer: B. Carolus Linnaeus

Explanation: Carolus Linnaeus introduced the binomial nomenclature system and laid the foundation of modern biological classification.