Question

What is the correct sequence of the complementary strand for the given portion of a DNA molecule:- 5' - G A C G T A C -3' ?

• A. 3' - T T G C A T G - 5'
• B. 3' - C T G C A T C - 5'
• C. 3' - C T G C A T G - 5'
• D. 3' - C T G T A T G - 5'

Hint:

Pair A with T and G with C, and write the new strand in the opposite direction.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The two strands of DNA are antiparallel and complementary. Adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C).

Step 2: Pair each base:
Given strand: \(5'\) G A C G T A C \(3'\).
G pairs with C, A with T, C with G, G with C, T with A, A with T, C with G.
The complement written along the same direction is: C T G C A T G, and it runs from \(3'\) to \(5'\).

Step 3: Result:
Complementary strand: \(3'\) C T G C A T G \(5'\). This is option C.
Option A uses T instead of C in the first position. Options B and D each have a base pair error (for example, ending in C or having T in place of C).

Final Answer:
The complementary strand is \(3'\)-CTGCATG-\(5'\), option (C). \[ \boxed{3'\text{-CTGCATG-}5'} \]