Table of Contents
Biomolecules Gateway Page
Jmol Tutorial

In this module:

Polymerization of Nucleotides
Base Pairing 1
Base Pairing 2
Complementary Sequences

DNA Replication

"It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material."

With this modest understatement, Watson and Crick introduced the second major discovery brought about by an understanding of DNA's structure, the mechanism by which DNA makes copies of, or replicates , itself. Finally, a mechanism for understanding how traits are passed on from parent to child was apparent.

Click on the step numbers below to see the steps in DNA replication. Click on the mouse at left to clear the images and text.


The strands of the double helix of DNA separate.


Enzymes catalyze the synthesis of new DNA in the 5' to 3' direction, using the original strands as models, or templates, for the complementary strands.


Two complete DNA molecules, each an exact copy of the original, are the result.

Because of the specificity of base pairing and a proofreading activity of the enzyme that synthesizes new DNA, less than one error in 100 million is incorporated into the new DNA strands. Thus genetic information is passed accurately on to the next generation.