DNA Replication

Roles of enzymes:

-Helicase: moves along a double-helical DNA, breaks the hydrogenbonds between two strands, unwinds the helix, and creates a replication fork.

-Single-stranded binding proteins: anneal to each single-stranded DNA immediately after it is unwinded by helicase to prevent it from reannealing.

-Gyrase: relieves the tension created by the unwinding of DNA at the replication fork by cutting the strands, letting them to rotate, and reconnecting them.

-Primase: builds short segments of RNA (primers), which are used by DNA polymerase III for elongation.

-DNA polymerase III: adds appropriate deoxyribonucleoside triphosphate to the 3' end of a parent strand, thereby creating a daughter strand in the direction of 5' carbon to 3' carbon. In each replication bubble, there is one leading strand and one lagging strand; the leading strand replicates towards the replication fork, the lagging strand replicates away from the fork. The leading strand is built continuously, whereas the lagging strand consists of many short segments of DNA called Okazaki fragments.

-DNA polymerase I: replaces the RNA primers in each Okazaki fragment and in the leading strand with corresponding DNA.

-DNA ligase: connects the Okazaki fragments by creating a phosphodiester bond.

-DNA polymerase I and DNA polymerase III also proofread the entire sequence, and fix any mistakes that were made in the replication process.

Here's a link that explains the replication process step-by-step.
A youtube video that gives an overview of the replication process.