What is the leading strand in DNA replication?

What is the leading strand in DNA replication?

• A. The strand that is continuously synthesized in the 5' to 3' direction.
• B. The strand synthesized in fragments away from the replication fork.
• C. The strand formed during transcription.
• D. The strand that is degraded first.

Answer: (A)

The main idea here is how DNA is copied: DNA polymerase can only add new nucleotides to a growing strand in the 5' to 3' direction. The leading strand is the one that can be copied in one continuous piece toward the replication fork, because its template runs 3' to 5' in that direction, allowing uninterrupted synthesis. That’s why it’s described as being continuously synthesized in the 5' to 3' direction. The other strand is made discontinuously as Okazaki fragments away from the fork, which is the opposite situation. Transcription involves creating RNA, not this DNA replication process, and degradation isn’t a defining feature of the leading strand.

The main idea here is how DNA is copied: DNA polymerase can only add new nucleotides to a growing strand in the 5' to 3' direction. The leading strand is the one that can be copied in one continuous piece toward the replication fork, because its template runs 3' to 5' in that direction, allowing uninterrupted synthesis. That’s why it’s described as being continuously synthesized in the 5' to 3' direction. The other strand is made discontinuously as Okazaki fragments away from the fork, which is the opposite situation. Transcription involves creating RNA, not this DNA replication process, and degradation isn’t a defining feature of the leading strand.