Which DNA strand is synthesized discontinuously and elongates away from the replication fork?

• A. Lagging strand
• B. Leading strand
• C. Okazaki fragment
• D. Template strand

Answer: (A)

The main idea is that DNA polymerase can only synthesize DNA in the 5' to 3' direction, and the two strands run antiparallel. One template runs 3' to 5' toward the fork, so it’s copied continuously as the fork opens—this is the leading strand. The other template runs 5' to 3' toward the fork, so synthesis must occur in short segments away from the fork, producing the lagging strand in pieces that are later joined. Therefore, the strand that is synthesized discontinuously and elongates away from the replication fork is the lagging strand. The short fragments you hear about are called Okazaki fragments, which are parts of this strand, not the strand itself. The template strand is the guide used for synthesis, not the product strand.