Question

Assertion (A): The sugar-phosphate backbone of two chains in DNA double helix shows anti-parallel polarity.
Reason (R): The phosphor-diester bonds in one strand go from a 3’ carbon of one nucleotide to a 5’ carbon of adjacent nucleotide, whereas those in complementary strand go vice versa.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
• C. (A) is true, but (R) is false.
• D. (A) is false, but (R) is true.

Hint:

The anti-parallel arrangement of DNA strands is essential for complementary base pairing and replication.

Answer 1

The Correct Option is A

\begin{itemize} \item DNA strands run anti-parallel, with one in 5’ to 3’ and the complementary strand in 3’ to 5’. \item The phosphor-diester bond arrangement described in Reason (R) explains the anti-parallel polarity of DNA strands, confirming the explanation of Assertion (A). \end{itemize} % Quick tip