Abstract: Described is a novel family of DNA polymerases identified in bacteriophages (mainly from the family of Siphiroviridae) which are able to accept 2-amino-2?-deoxyadenosine 5?-triphosphate (dZTP) as a substrate but which do not accept deoxyadenosine 5?-triphosphate (dATP) as a substrate. Also described are recombinant nucleic acid molecules, encoding such polymerases, vectors comprising such nucleic acid molecules, host cells transformed with such nucleic acid molecules or vectors as well as to methods for producing DNA molecules containing 2-amino-2?-deoxyadenosine (dZ) instead of 2?-deoxyadenosine (dA) by making use of a novel polymerase.