In what direction is the lagging strand synthesized during DNA replication?

The lagging strand is synthesized away from the replication fork during DNA replication due to the antiparallel structure of DNA. DNA polymerase, the enzyme responsible for synthesizing new DNA strands, can only add nucleotides to the 3' end of a growing DNA strand. Since the two strands of DNA at the replication fork are oriented in opposite directions, the lagging strand must be synthesized in short segments known as Okazaki fragments.

As the replication fork opens up, the lagging strand is synthesized in a direction that is opposite to the movement of the fork. This means that while the leading strand is continuously synthesized in the direction of the fork, the lagging strand is made in small pieces, which are later joined together, effectively causing its synthesis to occur away from the fork itself. This process allows for the overall simultaneous replication of both strands despite their differing synthesis orientations.

The fact that the lagging strand is synthesized in a discontinuous manner, creating short fragments, further emphasizes the need for this directional synthesis away from the replication fork to accommodate the mechanics of DNA polymerase.