2.Molecular Biology A.Background Chemical Bases in DNA DNA exists as two long,p paired strands spiraled into the famous double helix: ·Each strand is made up of millions of chemical building blocks called bases. Gene There are only four different chemical bases in DNA (Adenine, Thymine,Cytosine,and Guanine). DNA Molecule Chemical They can be arranged and Bases rearranged in countless ways. The order in which the bases occur determines the messages to be conveyed.• Each strand is made up of millions of chemical building blocks called bases. • There are only four different chemical bases in DNA ( Adenine, Thymine, Cytosine, and Guanine). • They can be arranged and rearranged in countless ways. • The order in which the bases occur determines the messages to be conveyed. Chemical Bases in DNA DNA exists as two long, paired strands spiraled into the famous double helix: 2. Molecular Biology A. Background