Here's why:
* DNA replication begins at an origin of replication. This origin is a specific sequence of DNA that is recognized by proteins involved in the replication process.
* DNA denatures at the origin. This means the two strands of the double helix separate, forming a "bubble" where the DNA is single-stranded.
* Replication forks form at each end of the bubble. Each replication fork is a Y-shaped structure where the DNA is being unwound and copied. The two replication forks move in opposite directions along the DNA molecule.
So, one origin of replication leads to two replication forks, allowing for simultaneous DNA replication in both directions.
