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Everyone talks about how DNA is the "molecule of life" and "the set of instructions for building you." How complete are the instructions, really, though? To make the question concrete, say I were to remove all of the DNA from a bacterium and replace it with the nuclear DNA from a eukaryote, would the cell (and it's daughters) be able to transition into the same sort of eukaryote as the DNA source? Granted, the lack of mitochondria would be a huge hindrance, but assume we could add some when the bacteria swelled up to a large enough size to accomodate them inside of it. Are there other barriers to this process?

I know that adding any single gene for producing a protein would function as expected when added to a bacterium, but would the lack of a nucleus and organelles prove fatal, or does the nuclear DNA have the information needed to build them up using only the machinery available in a bacterium?

What about an archaea? Or going the other direction - remove the nucleus from a eukaryote, add bacterial DNA, does the cell and its daughters survive to become bacteria?

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    $\begingroup$ If you want an analogy, it would be like having a hard drive containing all the specifications for all of the hardware and software necessary to read the information on the drive, as well as the manufacturing instructions for all of the machinery need to manufacture the computer, to manufacture the machinery needed to manufacture the machinery to manufacture the computer, and down the line to extraction of raw resources. The information is 100% complete, and totally sufficient to build a second set of all the machinery, but can't do it if you are just holding the bare drive. $\endgroup$
    – Bryan Krause ♦
    Jun 22, 2017 at 16:14
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    $\begingroup$ Barrier? Yes Prokaryotic and eukaryotic cells differ in DNA replication. So a prokaryotic cell would never replicate to form a eukaryotic cell. As of Mitochondria, Mitochondria have their own DNA and would replicate normally. I am not so sure about swapping with Archae though $\endgroup$
    – Soura
    Jul 24, 2017 at 11:44
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    $\begingroup$ @Soura Not to mention, bacterial DNA is partially methylated. Replacing bacterial DNA with the DNA from some eukaryote would not even if only for the reason that bacterial replication machinery requires this methylation. $\endgroup$
    – forest
    Mar 22, 2018 at 21:57

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This is a good question, because the answer to the overall question (is the information in DNA complete - yes) is not the same as the one to the more specific ones (would a cell survive if the DNA was swapped with that of another life form - no). Let me elaborate:

The information in the DNA of in any given organisms (except for a virus) IS complete. This means that the DNA has 'code' for all the molecules required to build and sustain this organism.

However, the DNA of an organism alone (or placed inside an unnatural environment like a completely different cell) is not sufficient to actually make or build that organism. The reason for this is that, while the DNA has all the necessary code, without the correct machinery to actually read that code nothing can or will happen. Eukaryotes and bacteria are so vastly different (which is to be expected after millions of years of evolution for both), basically all the different machineries are not compatible anymore: transcription binding sites are different, gene structure (exons/introns vs. operons) is different, Ribosomes are different, ... [btw this also means that just putting the gene of an eukaryote into a bacterium doesn't work, researchers have to modify it accordingly to work].
Even between different eukaryotes (and probably some bacteria but I'm not sure about that) exchanging the nuclear DNA would not produce viable cells (or at least not ones that could grow into an organism), since again the transcription machinery would not match up sufficiently.

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  • $\begingroup$ "[btw this also means that just putting the gene of an eukaryote into a bacterium doesn't work, researchers have to modify it accordingly to work]" Thanks, in particular, for clearing up that misconception of mine. Is it a difference in the codon to peptide mapping, or maybe something in how the dynamics of folding work? $\endgroup$
    – Sean Lake
    Jun 22, 2017 at 20:00
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    $\begingroup$ @SeanLake The main problem is the difference in gene structure (bacteria don't have introns). Codon usage (the frequencies of individual codons, not their meaning) can make problems, but will not prevent expression. Folding problems can also exist, but you can still make pretty much eukaryote protein in bacteria - just not necessarily always functional/correctly folded. $\endgroup$
    – Nicolai
    Jun 23, 2017 at 1:36

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