Synthesis of the leading and lagging strands

For the leading strand, DNA primase synthesizes an RNA primer at the origin, and then the leading strand is made in the same direction as the movement of the fork. Later, the RNA primer is removed, and the resulting gap is filled by DNA polymerase and connected by DNA ligase. In the lagging strand, primase periodically synthesizes an RNA primer near the opening of the replication fork, and then DNA polymerase synthesizes a short DNA fragment in a direction away from the fork. The RNA primers are removed by DNA polymerase, which also fills in the vacant region with DNA. Finally, DNA ligase connects adjacent Okazaki fragments.