As the two parental (template) DNA strands separate at a replication fork, each of the strands is separately copied by a DNA polymerase III (orange), producing two new daughter strands (light blue), each complementary to its respective parental strand. Because the two parental strands are antiparallel, the two new strands (the leading and lagging strands) cannot be synthesized in the same way. Drag each phrase to the appropriate bin depending on whether it describes the synthesis of the leading strand, the synthesis of the lagging strand, or the synthesis of both strands. a. multiple primers needed b. daughter strand elongates toward replication fork c. only one primer needed d. synthesized 5' to 3' e. daughter strand elongates away from replication fork f. made continuously g. made in segments

Synthesis of leading strand:

daughter strand elongate towards replication fork

only one primer is needed

made continuously

Synthesis of the lagging strand:

multiple primers needed

daughter strand elongates away from replication fork

made in segments

Synthesis of both:

synthesized in 5' to 3'

Explanation:

The replication of DNA involves the unwinding of the double helix structure by the helicase enzyme after which RNA primer binds to form a bubble known as the replication fork.

DNA can only be replicated in the 5' to 3' direction because the polymerase that is responsible for the elongation of new strands can only add nucleotides in the 5' to 3' direction.

Hence, the leading strand is replicated continuously in this direction while the lagging strand is replicated discontinuously or fragments known as the okazaki fragments. The discontinuous replication of the lagging strand therefore requires different primers biding at multiple sites on the DNA strand.

Because of the nature of replication of the lagging strand, the elongation of the fragments moves away from the replication fork while that of the leading strand moves towards the replication fork.