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Wiki says

DNA is a molecule that carries most of the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses.

What bugs me is the "most" there, it implies some of the genetic instructions are elsewhere, but where?

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    $\begingroup$ Are all _____ instructions in DNA.. Genetic: yes. Inheritable: no. $\endgroup$ – WYSIWYG Jun 27 '16 at 8:34
  • $\begingroup$ Would you please expand on that, or give me a general direction on where to look for? $\endgroup$ – erik Jun 27 '16 at 8:38
  • $\begingroup$ maybe you mean histone modification $\endgroup$ – A. Steiner Jun 27 '16 at 8:51
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    $\begingroup$ Genetic information specifically means DNA or RNA in case of certain viruses. There are, however, other information that can be inherited which include cytoplasmic factors like mRNAs, proteins, vesicles etc. Check maternal inheritance. $\endgroup$ – WYSIWYG Jun 27 '16 at 9:15
  • $\begingroup$ Generally, in Biology it is better to use "most". Because we can't be sure that we have done a complete research about it. And about your question: Yes. But note that the whole genetic instructions are NOT located in the Nucleus(of course, in eukaryotic cells like ours). Also note that some genes like Metabolic Enzymes's Genes are located in the Mitochondria(and the Chloroplast in Plant cells). $\endgroup$ – YJB Jun 27 '16 at 16:59
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Genetic information is the heritable information used by organisms to guide their self-assembly. It's why traits can persist across generations. DNA is, by far, the primary material used (by life) to encode genetic information, but it's not the only one. RNA is a pretty common alternative to DNA.

If we're looking to Wikipedia, this is actually referred to (in passing) on many pages about genetics. They usually link to the page on the best known edge case, RNA viruses:

An RNA virus is a virus that has RNA (ribonucleic acid) as its genetic material. This nucleic acid is usually single-stranded RNA (ssRNA) but may be double-stranded RNA (dsRNA). Notable human diseases caused by RNA viruses include Ebola hemorrhoragic fever, SARS, influenza, hepatitis C, West Nile fever, polio, and measles.

While viruses fall into a weird middle ground between life and inanimacy, they still all need genes, and many of them use RNA for that. Side note: retroviruses get their name from the fact that they use reverse transcription to synthesize DNA from an RNA template.

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  • $\begingroup$ I guess that's excluded where it says "many viruses" instead of "all viruses" $\endgroup$ – erik Jun 27 '16 at 23:49
  • $\begingroup$ I'm not sure what you're referring to being excluded (too many pronouns), but 1) biology is full of exceptions, and 2) many viruses store their genes in DNA. $\endgroup$ – CircleSquared Jun 28 '16 at 2:33
  • $\begingroup$ RNA is an alternative, not a complement, by using "many viruses" I think wiki rules out RNA viruses from that sentence. The use of "most" suggests that there is a complement. About mitochondrial DNA, it's still DNA. So it probably is just a wording mistake in wiki or a misinterpretation by me as so far I know of no such complement. $\endgroup$ – erik Jun 28 '16 at 18:45
  • $\begingroup$ @erik Maternal effect genes during embryonic development are set up in the oocyte prior to fertilization on mRNA. Obviously these genes are found on maternal chromosomes (DNA), but they are not expressed by the oocyte or the embryo, so technically the instructions are stored on RNA and the RNA is heritable, They may also be referring to epigenetic modifications, though there is still a bit more controversy about whether or not those are heritable. $\endgroup$ – AMR Jun 29 '16 at 17:59

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