I was thinking about a fiction world in which all animal (at least vertebrate) could crossbred because they share same number and layout of chromosome but differ in hereditary detail (like human skin color) and/or using epigenetic modifications.

Is it actually possible? And how large of DNA it could be to code all vertebrate form and function?

I'm programmer so I just think DNA as a code. And it seem we could refactor and reuse most of DNA code between tetrapod species (also between arthropod-arthropod species)

  • $\begingroup$ I don't really understand your question. Are you asking something like "what is the Shanon's entropy of all vertebrates DNA put together?" $\endgroup$
    – Remi.b
    Sep 14 '16 at 3:27
  • $\begingroup$ Cell fusions could be done in plants; don't know does it happen to animals or not. Usually animals can't support chromosomal aberration. They die. But most plants can easily support chromosomal aberration. $\endgroup$ Sep 14 '16 at 10:52
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    $\begingroup$ The very similarities in number and layout of chromosomes that allows animals to breed with each other are the same similarities that cause them to end up with reasonably similar phenotypes. As soon as the genomes are too different to breed with each other, the phenotypes of the animals are so different that we categorise them as different species (usually). Therefore, I believe the question that you're really asking is, "can epigenetic control alone result in phenotypes so different that they would seem like different species?" $\endgroup$
    – Armatus
    Sep 16 '16 at 15:08
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    $\begingroup$ Probably the OP is asking "is it possible to write/formulate a general genetic-scheme for a group-of-organism (say all vertebrates)?". Is that? $\endgroup$ Sep 17 '16 at 14:44
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    $\begingroup$ @AlwaysConfused I press upvote at your right comment. As I was state that I am thinking about fictional alien (parallel) world, I just want it scientifically possible $\endgroup$
    – Thaina
    Sep 17 '16 at 15:22

Suppose genome A generates organism oA and genome B generates organism oB. Their phenotypes pA and pB are quite different from each other.

Because genome A and B are not similar enough, organism oA and oB cannot sexually produce viable offspring.

Your question seems to boil down to: "Would it be possible to generate oA/pA and oB/pB from genome A, or a genome similar enough to genome A such that it can still sexually reproduce with genome A?"

So you basically ask whether any genome A could simultaneously produce pA and pB under different external conditions.

Answer: Possibly? The genes involved in the development of organisms typically don't respond to external stimuli but to genes which were active before them (in time). Various genes produce proteins which sense temperature, osmotic pressure or particular chemical species or ions. If those were factored into very early developmental programs, feeding into transcription factors to modify gene expression according to external factors, the same genome could produce drastically different organisms.

To speculate more about this yourself, it would probably help to go away from a code-based understanding of DNA and think more about what it is physically and biologically. Unlike computer programs, DNA "programs" can modify themselves and other programs or the functions they execute.

Biologically, DNA is an information carrier that is transcribed into RNA, which can have functions of its own and/or be translated into proteins. DNA interacts very tightly (physically) with a lot of RNA and protein components, and most things that happen in cells and tissues around them end up modifying the way DNA is handled in some way. Keywords that you could look up are "gene expression", "gene regulation" and "developmental biology".


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