The initiation of DNA replication starts at the tail end of the previous cell division and continues through the cell cycle phase known as G1. DNA synthesis happens during the S phase. Levels of a protein called CDK are critical to ensuring that DNA is replicated once and only once. When CDK levels are low, helicases can jump onto the DNA and start to unwind it. But repeat binding does not happen because CDK levels rise, and this blocks the helicase from binding again.

Project: Creation of graphic to accompany article.
Client: Knowable Magazine