What is the lagging strand in DNA replication?

What is the lagging strand in DNA replication?

• A. The strand synthesized continuously from 3' to 5' direction.
• B. The strand that is synthesized in fragments away from the replication fork.
• C. The strand that unwinds first.
• D. The strand that serves as the template.

Answer: (B)

DNA polymerase can only add nucleotides to a free 3' end, so new DNA grows in the 5' to 3' direction. With the two parental strands running antiparallel, one strand can be copied continuously toward the fork (the leading strand), while the other must be built in short stretches away from the fork in the opposite direction; these short segments are Okazaki fragments and are later joined to form a complete strand. So the lagging strand is the one synthesized in fragments away from the replication fork. The other options don’t fit this pattern: unwinding is done by helicase on both strands, both strands serve as templates, and synthesis occurs 5' to 3' rather than 3' to 5' on the new strand.

DNA polymerase can only add nucleotides to a free 3' end, so new DNA grows in the 5' to 3' direction. With the two parental strands running antiparallel, one strand can be copied continuously toward the fork (the leading strand), while the other must be built in short stretches away from the fork in the opposite direction; these short segments are Okazaki fragments and are later joined to form a complete strand. So the lagging strand is the one synthesized in fragments away from the replication fork. The other options don’t fit this pattern: unwinding is done by helicase on both strands, both strands serve as templates, and synthesis occurs 5' to 3' rather than 3' to 5' on the new strand.