This 3D animation shows you how DNA is copied in a cell. It shows how both strands of the DNA helix are unzipped and copied to produce two identical DNA molecules. 

This 3D animation shows you how DNA is copied by the cell, a process called DNA replication.

We start by seeing the DNA double helix being unzipped to form a replication fork. We then follow DNA polymerase as it copies the DNA in the 5’ to 3’ direction using the existing DNA as a template.  The leading strand is constructed in a continuous fashion while the lagging strand is made discontinuously, in a series of short fragments of DNA called Okazaki fragments.