Which DNA strand is continually synthesized by DNA polymerase?

Which DNA strand is continually synthesized by DNA polymerase?

• A. Lagging strand
• B. Coding strand
• C. Template strand
• D. Leading strand

Answer: (D)

DNA polymerase can only synthesize DNA in the 5' to 3' direction. As the replication fork opens, one strand runs 3' to 5' toward the fork, so synthesis on this template can proceed continuously in the same direction as the fork movement. This is the leading strand, built in one uninterrupted stretch. The opposite template runs 5' to 3' toward the fork, so synthesis must occur in short segments (Okazaki fragments) away from the fork, with primers added and later joined, making it the lagging strand. The terms template and coding strands are more relevant to transcription, and during replication both strands can serve as templates depending on the region, so they aren’t fixed in the same way as the leading vs lagging distinction.

DNA polymerase can only synthesize DNA in the 5' to 3' direction. As the replication fork opens, one strand runs 3' to 5' toward the fork, so synthesis on this template can proceed continuously in the same direction as the fork movement. This is the leading strand, built in one uninterrupted stretch. The opposite template runs 5' to 3' toward the fork, so synthesis must occur in short segments (Okazaki fragments) away from the fork, with primers added and later joined, making it the lagging strand. The terms template and coding strands are more relevant to transcription, and during replication both strands can serve as templates depending on the region, so they aren’t fixed in the same way as the leading vs lagging distinction.