Sequencing of DNA has been revolutionized by the advent of dideoxynucleotides and the Sequenase enzyme. Dideoxynucleotide triphosphates are readily incorporated into a growing DNA chain, but lack the 3′ hydroxyl group necessary to allow the chain to continue, and effectively terminate polymerization. Sequenase is a T7 DNA polymerase that has been chemically (Sequenase 1.0) or genetically (Sequenase 2.0) modified to remove its 3′–5′ exonuclease activity (Fuller et al., 1996). Sequencing DNA