DNA Replication: A Closer Look * The copying of DNA is remarkable in its speed and accuracy * More than a dozen enzymes and other proteins participate in DNA replication Getting Started * Replication begins at particular sites called origins of replication, where the two DNA strands are separated, opening up a replication ?bubble? * A eukaryotic chromosome may have hundreds or even thousands of origins of replication * Replication proceeds in both directions from each origin, until the entire molecule is copied * At the end of each replication bubble is a replication fork, a Y-shaped region where new DNA strands are elongating * Helicases are enzymes that untwist the double helix at the replication forks * Single-strand binding proteins bind to and stabilize single-stranded DNA