Prime purpose of this lecture is to present on Recombinant DNA and Polymerase Chain Reactions. DNA – Double Helix Structure; Each spiral strand is composed of a sugar phosphate backbone and attached bases; 4 Bases: Adenine (A), Guanine(G), Cytosine (C), and Thymine (T). Recombinant DNA molecules are DNA molecules formed by laboratory methods of genetic recombination to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in the genome.