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BiologyGenetics11 minIntermediate

DNA Replication Fork

Follow the enzymes and strand geometry that let DNA copy both strands from a moving fork.

Annotated teaching image of a DNA replication fork with helicase, leading strand, lagging strand, and primers.
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Replication fork

The Y-shaped region where DNA strands separate and copying begins.

DNA replication copies both strands, but DNA polymerase can only extend in one chemical direction. That creates a continuous leading strand and a segmented lagging strand.

Helicase opens the fork, binding proteins stabilize single strands, polymerases copy DNA, and primers provide starting points for new synthesis.

Key Idea

The replication fork is a coordinated machine. Its geometry explains why the two new strands are built differently.