Leading & Lagging strands:

DNA is replicated by continuous synthesis of a leading strand and discontinuous synthesis of a lagging strand of the DNA molecule.The polymerase at the leading strand template remains attached to the DNA, continuously synthesizing the leading strand.Coordination between leading and lagging strand synthesis is achieved by the dimerization of DNA polymerase molecules at the replication fork.The lagging strand polymerase initiates DNA synthesis at the fork, from an RNA primer made by a primase complex.Once the polymerase completes an Okazaki fragment, it dissociates from the DNA template.The polymerase reassociates with the template at this position, to continue synthesis of the lagging strand.By this mechanism, the two polymerases can add nucleotides to the growing strands at the same time, and at rates up to 1000 base pairs per second.The polymerase elongates the lagging strand in a direction opposite the fork, but stays bound at the fork.The DNA polymerase dimer moves with the replication fork.A new primer is produced at the fork.