reminds me of the terms "artitificial intelligence".
i'm making an assumption here. i think the term natural dna refers to the natural progression and evolution of dna due to internal processes
reactions to the external environment.
and synthetic dna may refer to dna that is altered via outside intelligence(s), or the manipulation of environment and the effects it has with
programming dna over a short period of time, or over a long period of exposure to manipulated environment(s).