Watson-Crick base pairing

Watson- Crick base pairing 

Background

In 1953, James D Watson and Francis Crick discovered the structure of DNA using X ray Crystallography. They worked out that DNA was a double helix using Rosalind Franklin's X ray diffraction pattern. At first, it was thought that DNA was made up of many chemicals, which proved too difficult to analyse, but the researchers persisitence led to the discovery of complementary base pairing.