Is DNA universal?

I had a question come to me this morning, and I’m not sure about the answer.

Is DNA universal?  If life evolves on a completely different planet, would it have DNA molecules just like ours, or would it evolve a completely different protein structure for its “code of life” than what evolved here?

This is a closeup of a DNA molecule.

DNA Structure
DNA Structure

This picture (swiped from Wikipedia) is included here because it illustrates a point — DNA does not have an elegantly simple structure.  It is a complex protein, but one thing I do not know is whether that complexity is actually justified, or if it is a result of the random processes which created the first building blocks of life.  Perhaps a simpler protein would have more transcription errors, and this design is more resistant to those problems.

I believe that if life were to evolve elsewhere, it would need to have a way to store genetic information like DNA does, but it would probably have a very different protein structure for storing that information.  I’m guessing that it would have a similar level of complexity to DNA, though.

The Stargate SG-1 episode “Hathor” has a premise that’s incompatible with my thoughts.

Stargate SG-1: Hathor

A related question:  Would we be able to eat plants and animals that evolved on another planet, or would their chemical structures be just different enough from ours that our digestive systems would not be able to find any useful molecules?

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elyograg

Faced with the choice between changing one's mind and proving that there is no need to do so, almost everyone gets busy with the proof. -- J.K. Galbraith

One thought on “Is DNA universal?”

  1. My best guess is that
    – RNA might be a general building block in life, since its components are so stable that they are even build in space:
    http://news.softpedia.com/news/DNA-and-RNA-Came-from-Space-88016.shtml
    – DNA might be absent in higher life-forms on different planets (see for example some viruses on earth)
    – Life forms on different planets will probably have proteins, since they allow a chemical building block system with a huge set of combinatorial combinations and thus are highly adaptable for different tasks. But other life forms will probably have a different set of amino acids that are used (See Non-standard amino acids in https://en.wikipedia.org/wiki/Amino_acid)
    – You could might be able to digest some materials of a extraterrestrial life-form, but just think of Cellulose: Its a major source of carbohydrates and still cant use it…
    Next there are things like chirality:
    https://en.wikipedia.org/wiki/Chirality_%28chemistry%29
    Even if an extraterrestrial life form would have carbohydrates that have the same overall structure, chirality could prevent your enzymes from splitting them into digestible parts.

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