Simultaneous, parallel synthesis of leading and lagging strands

Some diagrams of DNA replication show leading and lagging strand synthesis as under the control of two different DNA Polymerase molecules. In fact, replication is controlled by a single, dimeric enzyme, and is oriented such that extension in the 5'3' direction occurs in parallel. The lagging strand is wrapped around one of the subunits, and passes through it in parallel to the leading strand.

Figure © 2012 TA Brown, Introduction to Genetics (1st ed.); additional text © 2014 by Steven M. Carr