Answer: cytosine.
- A cytosine
- B thymine
- C adenine
- D uracil
Correct answer: A. cytosine
Explanation: Guanine pairs with cytosine (G–C).
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.