How long ago did DNA start to include sequences that code for protein?
closed as too broad by David, AliceD♦, kmm, fileunderwater, James Feb 2 '17 at 3:56
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There are two questions being asked here.
1) When DNA was used to encode RNA via DNA dependent RNA polymerase It is uncertain if the Last Universal Common Ancestor (LUCA) had this enzyme. There is some debate.
Also some DNA polymerases of family A, B are structurally related to RNA polymerases https://www.ncbi.nlm.nih.gov/books/NBK6360/. So DNA may have come after RNA. The switch to DNA has been proposed to be a result from a reaction to the evolution of RNAse.
2) When RNA was used to encode protein via ribosome LUCA has ribosome. So LUCA had proteins made from RNA https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2926754/
And LUCA has been estimated to have appear around 3.5-3.8 billion years ago. https://en.wikipedia.org/wiki/Last_universal_common_ancestor