DNA polymerases catalyze the synthesis of DNA molecules from monomeric deoxynucleotide triphosphate units. This definition encompasses those enzymes classed as DNA-dependent DNA polymerases (EC 2.7.7.7, which require both a DNA template strand and a DNA primer to which the monomeric units can be added), reverse transcriptases (EC 2.7.7.49, RNA-dependent DNA polymerases that utilize an RNA template), and terminal deoxynucleotidyl transferases (EC 2.7.7.31, which require no template). This chapter will consider only DNA-dependent DNA polymerases (EC 2.7.7.7, DNA nucleotidyltransferases, DNA-directed).
