Which of the following statements are true regarding a normal double stranded DNA molecule found in eukaryotes?
(A) The two strands are held together by disulfide bond.
(B) Base component follows the Chargaff’s rule where the ratio of \( \displaystyle \frac{A+G}{T+C} = 1 \)
(C) The two chains are coiled in a right-handed fashion.
(D) DNA replication is a conservative process resulting in one old and one new strand.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (B) and (C) only
(A) The two strands are held together by disulfide bond. — Incorrect. The two strands are held together by hydrogen bonds between the bases, two between A and T and three between G and C.
(B) Base component follows the Chargaff’s rule where the ratio of \( \displaystyle \frac{A+G}{T+C} = 1 \) — Correct. By Chargaff’s rule, A equals T and G equals C. So the purines (A + G) equal the pyrimidines (T + C), and the ratio is 1.
(C) The two chains are coiled in a right-handed fashion. — Correct. The two antiparallel chains form a right-handed double helix.
(D) DNA replication is a conservative process resulting in one old and one new strand. — Incorrect. Replication is semi-conservative. Each daughter DNA gets one old and one new strand. A conservative process would keep both old strands together in one molecule.