Answer: It adds nucleotides only in the 5 prime to 3 prime direction on the new strand.
- A It adds nucleotides only in the 5 prime to 3 prime direction on the new strand
- B It adds nucleotides only in the 3 prime to 5 prime direction on the new strand
- C It synthesises both strands in the 3 prime to 5 prime direction
- D Direction depends on which strand is being copied
Correct answer: A. It adds nucleotides only in the 5 prime to 3 prime direction on the new strand
Explanation: DNA polymerase always extends a new strand in the 5 prime to 3 prime direction, regardless of which template strand is being copied; this is why one strand is synthesised continuously and the other discontinuously.
Helicase unwinds the double helix at the replication fork; one new strand (leading) is synthesised continuously toward the fork, while the other (lagging) must be made in short, separate Okazaki fragments because DNA polymerase only adds nucleotides 5'→3'.
Concept context
DNA structure, replication, transcription, translation, the genetic code, and gene regulation (lac operon). The single most important chapter for NEET molecular biology.