Interdisciplinary Note (13 of 25)
Bacteria possess circular chromosomes. Replication begins at an origin or replication with binding and assistance of a cohort of proteins which lead to unwinding of the template DNA and RNA primer synthesis. Replication then proceeds in opposite directions on the two strands carried out mainly by DNA polymerase III. A site where the DNA is being unwound and new DNA synthesized is called a replication fork. At the replication fork, one strand, the leading strand, is synthesized in the 5' to 3' direction toward the replication fork, while the copy of the lagging strand is formed in the 5' to 3' direction in Okazaki fragments leading away from the replication fork. As replication proceeds, the Okazaki fragments are ligated forming one of the daughter strands.