Answer: double helix.
- A double helix
- B single line
- C round sphere
- D solid cube
Correct answer: A. double helix
Explanation: DNA has a twisted double-helix structure.
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.