In time the two started seeing patterns in other people’s research. There were consistencies in the research of Rosalind Franklin, the X-Rays from Wilkins, a proposed DNA model from a man named Sven Furberg, and , of course, the Chargaff ratios. The Chargaff ratio was the rule that DNA will include an equal amount of Guanine(G) and Cytosine(c), and the same for Adenine(A) and Thymine(T). Watson eventually saw that the two pairs were structurally complimentary, and they existed in equal amounts because they bonded to one another, as you can see in the illustration below:

Shortly after this puzzle piece moved into place, the whole picture came together and Watson and Crick completed their Double Helical structure for DNA. The Adenine, Thymine, Cytosine and Guanine could easily separate, breaking the structure in two so that the strands could replicate easily. This easy replication method made DNA perfect for the genetic carrier canidate science had been looking for. They had indeed discovered the secret of life.