An enzyme that catalyzes the synthesis of DNA. It does this by catalyzing the addition of deoxyribonucleotide residues to the free 3′-hydroxyl end of a DNA chain, starting from a mixture of the appropriate triphosphorylated bases, which are dATP, dGTP, dCTP and dTTP. This chemical reaction is reversible and, hence, DNA polymerase also functions as an exonuclease.