I study quite a lot of chemistry, biology, and other branches of those fields, alongside some forms of astronomy. As part of a large-scale project I have been working on for a few years and continue to do so, aiming to be as scientifically accurate as I can get that involves extraterrestrial lifeforms.

I have questioned whether or not it is possible for DNA and RNA to have completely different substitutes. Both compose of a sugar and phosphate backbone with a base, but I wondered if completely different molecules could take their place, functioning with at least a similar role of storing genetic information among native organisms on the planet. I am aware of a group of synthetically-made nucleic acids known as XNA exists, most of which containing a differing sugar backbone, but still retaining many of the structural components of DNA. Although there is room for variation among these (such as different bases, and a different amount of bases) I want to consider the possibility of a completely different composition altogether.

I figure it may be possible in the first place considering the differing chemical compositions in other planets' biospheres that may affect what concentrations of certain molecules are available. Whatever biomolecule in their place has to be ubiquitous, stack to create polymers, bond in certain ways and be replicatable in general, which it may be tricky to find another one that isn't the ones found in nucleic acids as we know them.

Both alternatives of the structure still using macromolecules we know, such as lipids, proteins and the sort, and the possible more theoretical ones of not using these at all are both what I'm open to. Any sort of other-worldly method genetic information could be stored, in a possibly scientifically accurate way, is mostly the topic at hand that I wish to find any answers on.

Is it possible? What could they be, if so, if that could even be answered? How specific they could be on their functions and make-up does not matter; the concept, if it could theoretically work, is what matters.

  • $\begingroup$ Hi Averian, I think we’ll need a little more clarification to give you some good answers. Are you hoping that we’ll re-use one of the already existing macromolecules (lipids, proteins etc) and obeying plausible natural chemical rules? Or are you hoping for something more outlandish, like a synthesized nitrogen-based crystal that holds information perfectly and can be accessed by biological life? $\endgroup$ – Dubukay Jul 7 '19 at 5:24
  • $\begingroup$ Please mind that a theoretical exercise to compile all the possible alternatives to ribonucleic acids it would be probably matter for a phew Phd's, and therefore makes this question too broad. $\endgroup$ – L.Dutch - Reinstate Monica Jul 7 '19 at 5:42
  • $\begingroup$ I suppose both in a way but also a plausible form of an outlandish one as well that does not use any of the macromolecules known to store genetic information. I will correct the question, thank you $\endgroup$ – Averian Jul 7 '19 at 18:04

TNA is a more compact form of genetic information storage that possibly was the predecessor of RNA, although this seems unlikely given the biochemical chaos that was early earth, since TNA requires a controlled lab environment and has never been observed in the natural world. RNA is a 'jack of all trades' molecule that can act as an enzyme and also a genetic information carrier, but TNA can also do the same. Where TNA differs is its sugar. TNA uses threose instead of RNA which uses ribose, and DNA which uses deoxyribose. And this is TNA's key advantage. Because of its different sugar makeup it is much smaller than its companions, making it easier to form. Researchers have already created a TNA molecule that can attach to a specific protein. This is the beginning to creating a TNA enzyme that can adjust and control a chemical reaction just like RNA.

There are many others, but the most likely and most basic form of genetic storage for the very first life forms on Earth were probably consisting of ANA strands. (amyloid nucleic acid)

Hope this helps!

  • $\begingroup$ can you explain what is TNA? $\endgroup$ – L.Dutch - Reinstate Monica Jul 7 '19 at 10:01
  • $\begingroup$ I thankfully already understand what TNA is and have done a good amount of research on it. I have not however really heard of ANA and I may consider what I can do with that. Thank you, I appreciate the answer. $\endgroup$ – Averian Jul 7 '19 at 18:11

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