While DNA can only replicate with the help of special proteins (enzymes), the synthesis of these proteins can only be realized by the information encoded in DNA. As they both depend on each other, they have to exist at the same time for replication. Science writer John Horgan explains the dilemma in this way: DNA cannot do its work, including forming more DNA, without the help of catalyticproteins, or enzymes. In short, proteins cannot form without DNA, but neither can DNA form without proteins.
