Question

DNA synthesis during replication is ______i_____ and RNA synthesis during transcription is_____ii_______.

• A. i- continuous, ii- semi-discontinuous
• B. i- semi-discontinuous, ii- semi-discontinuous
• C. i- semi-discontinuous, ii- continuous
• D. i- continuous, ii- continuous

Answer 1

The correct option is C i- semi-discontinuous, ii- continuous

DNA replication (DNA synthesis) takes place during the S phase (synthesis phase) of the cell cycle.

Replication takes place in 5' →3' direction only.

Out of the two strands of DNA, the template strand with 3' → 5' polarity can easily form a new continuous strand of DNA in 5' → 3' direction (leading strand).

The template strand with 5' → 3' polarity would be forming a semi-discontinuous strand (lagging strand) with multiple small fragments (okazaki fragments).

Because of this behaviour where one strand is synthesised continuously and the other strand is synthesized discontinuously, DNA synthesis during replication is semi- discontinuous.

Transcription is the copying of genetic information from one strand of DNA (template strand) to RNA. Transcription also takes place in a 5' → 3' direction only. As only one new strand of RNA needs to be synthesized, it is easily synthesized in a continuous manner in the 5' → 3' direction by using the 3'→ 5' DNA strand as a template. Therefore, RNA synthesis during transcription is a continuous process.