1. Which of the following enzymes is responsible for relieving the torsional strain produced ahead of the replication fork during DNA replication?

  • A. DNA ligase
  • B. Topoisomerase (DNA gyrase)
  • C. Primase
  • D. DNA polymerase III

Answer: B. Topoisomerase (DNA gyrase)

Explanation: Topoisomerase removes supercoiling ahead of the replication fork by cutting and rejoining DNA strands.

2. The bicuspid (mitral) valve is located between:

  • A. Right atrium and right ventricle
  • B. Left atrium and left ventricle
  • C. Left ventricle and aorta
  • D. Right ventricle and pulmonary artery

Answer: B. Left atrium and left ventricle

Explanation: The mitral valve prevents the backflow of blood from the left ventricle into the left atrium during ventricular contraction.

3. Which endocrine gland secretes melatonin?

  • A. Pituitary gland
  • B. Thyroid gland
  • C. Pineal gland
  • D. Adrenal gland

Answer: C. Pineal gland

Explanation: The pineal gland secretes melatonin, which regulates the circadian rhythm and sleep-wake cycle.

4. Which nitrogenous base is present only in DNA?

  • A. Uracil
  • B. Adenine
  • C. Thymine
  • D. Guanine

Answer: C. Thymine

Explanation: DNA contains thymine, whereas RNA contains uracil instead of thymine.

5. Which blood group is known as the universal recipient?

  • A. A
  • B. B
  • C. O
  • D. AB

Answer: D. AB

Explanation: Individuals with blood group AB possess both A and B antigens and lack anti-A and anti-B antibodies, making them universal recipients.

6. Which scientist proposed the theory of inheritance of acquired characters?

  • A. Charles Darwin
  • B. Hugo de Vries
  • C. Jean Baptiste Lamarck
  • D. Gregor Mendel

Answer: C. Jean Baptiste Lamarck

Explanation: Lamarck proposed that characters acquired during an organism's lifetime could be inherited by the next generation.

7. Which of the following is a biodegradable pollutant?

  • A. Plastic
  • B. DDT
  • C. Domestic sewage
  • D. Mercury

Answer: C. Domestic sewage

Explanation: Domestic sewage contains organic matter that can be decomposed by microorganisms, making it biodegradable.

8. Which part of the flower develops into a fruit after fertilization?

  • A. Ovule
  • B. Ovary
  • C. Style
  • D. Stigma

Answer: B. Ovary

Explanation: After fertilization, the ovary develops into the fruit, while the ovules become seeds.

9. Which type of RNA carries amino acids to the ribosome during protein synthesis?

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

Answer: C. tRNA

Explanation: Transfer RNA (tRNA) transports specific amino acids to the ribosome and recognizes codons through its anticodon.

10. Which of the following vitamins is also known as ascorbic acid?

  • A. Vitamin A
  • B. Vitamin B₁₂
  • C. Vitamin C
  • D. Vitamin E

Answer: C. Vitamin C

Explanation: Vitamin C (ascorbic acid) is a water-soluble vitamin essential for collagen synthesis, wound healing, and antioxidant activity.