Alright; this is a nitty-gritty, in-depth biology question (with no real CORRECT answer...) but I've been beating my head in without getting anywhere. I'll just ask the question now. If, like me, you don't have a clue, then you don't have to read any furthur:
What's a good hypothetical alternative to using nucleic acids as a storage device for a genome?
The reason I ask...
In my story I've got a highly adept and deadly alien entity constantly attacking this solar system (ie: Earth). The aliens' body cells are permanantly 'totipotent': they can 'infect' most living tissues on Earth and alter any nucleotide-based genetic structure to suit their own purposes.
The point is: these ravenous alien cells still rely on DNA-based data storage and they produce their proteins via nucleic acids. The only other type of nonterrestrial life in my story is a primitive saltwater ecosystem in the ocean of Europa. These guys are Carbon-based (like us) and constructed of similar proteins to Earth-based life, but they DON'T use nucleic acids to store or transcribe their genome: no DNA storage, no RNA transcription. For this reason, their genome cannot be 'subsumed' by the aliens.
I could just glance over the whole thing, but it does eventually become a major plot point, and not explaining at least a BIT of the chemistry would be awkward, so any insight is appreciated!
August 25th, 2006, 06:54 PM
Hmmmm, I dont see how you could have DNA storage without nucleoacids (biologically) unless they were completly crystalline, perhaps like crystal nanobots?
Also, you could maintain DNA by having your creatures contain triple helix DNA. This would mean only 1/3 of the info would be contained per strand, thus incompatable with strands requiring a 1/2 strand to blend.
August 25th, 2006, 06:55 PM
It's a good question... and really does need a professional.
It has to be something able to be produced naturally by a carbon-based lifeform so probably something we already know about altho... maybe it isn't, maybe it's something new since it will be doing a job that hasn't been done before. Maybe you need to invent something? Maybe there is something theoretical that you can borrow.
Remember the Tachyon Drive?
August 25th, 2006, 07:01 PM
Ah, yeah. I'd thought about a triple-helical structure. My problem is that I need something REALLY out there, ideally something not related to nucleotides at all. A 'crystaline' structure sounds intriguing; some kind of complex latticework, right? That way a large amount of data could be stored without resorting to nucleotide-sequencing (the problem, I bet, would be for the organism itself to 'acces' the data for transcription, but I don't plan on going THAT in depth...) its a neat direction to think about.
August 25th, 2006, 07:25 PM
How to access info from a crystalline structure = pressure. Pieso-electronics (sp?). Pressure on a quartz produces electricity ( ex: quartz watch)
September 15th, 2006, 06:37 PM
The crystalline structure thing is interesting, but there are only a certain number of crystal-y type shapes (I think--chemistry is not my strong point, but genetics is) so you'd still need components that differed in a nucleotide type way.
What about an entirely protein-based organism? It could reproduce its enzymes and structural elements using other very stable enzymes with the capability to 'read' the chain of amino acids. Antibodies can recognise sections/folds of proteins, and so it would take only a little altering at the other end to make them able to reproduce what they were 'reading'. Levels of the product could be easily controlled through similar method to DNA based organisms.
My tutor would probably cry if he knew I was suggesting this. :rolleyes:
September 17th, 2006, 12:17 AM
I'd thought about those very same constraints in crystals...
I like the protein idea: a LOT, actually! But my aggressive little alien cells have proteins, antibodies, etc... (one of the 'shockers' of my yarn is that the aliens are really TERRESTRIAL in origin...) so I'm afraid they could manage to corrupt even a fully-protein based system
well, for good or ill, though, I'm currently married to the crystal idea: *biological cells with a completely crystalline nucleus*.
Trust, me, though, my explanation of their function would make your tutor want to kill me ;)
I figure that the basic replicative units themselves are held in crystal lattice structure, and are activated or repressed through 'piezo-electrical' stimulation (that is, the crystals generate an electric current due to physical pressure exerted on them; this pressure on the lattice would be the trigger for mitotic division, as opposed to straight-up chemical signaling; maybe a constriction of the nuclear envelope in response to chemical signals **THANKS TO Dazzlinkat!!**). The genetic code would be 'read' off the current, and how the electricity travels through each crystal 'unit' would dictate how the biological cells are replicated (the voltage would change across the lattice depending on WHAT kind of molecules were embedded within the crystal-frame, effectively making the crystals units of data). Therefore the 't-RNA' that would transcribe DNA into proteins for OUR cells would essentially be a organelle akin to a voltometer in THEIR cells, able to read the constantly fluctuating electric signal, from which it would then produce biological proteins. (one assumes that these guys' cells would need to be much larger than your average Earth-based eukaryote, in order to hold such a sprawling crystal structure at its center).
This whole idea is shakier than a Soviet space shuttle, but it's not COMPLETELY laughable (at least, not to people with only a rudimentary understanding of cellular replication) and it certainly makes the things different enough for my purposes. I've even thought of a tongue-in-cheek name for these little guys: the 'Crystalline Entities' (that's for all you hard-core Star Trek: TNG fans).
September 17th, 2006, 04:20 PM
I think it's quite scary that I understood all that!
You've convinced me that the crystal thing is viable. It sounds a bit like a sort of biological computer. Also, higher level organisms of that type would probably be able to absorb a wider range of molcules, and thus store more information. Now I'm getting carried away ... :D
September 17th, 2006, 05:15 PM
how the electricity travels through each crystal 'unit' would dictate how the biological cells are replicated
Hmmmm ... shapeshifters? Or at least, the ability to adapt to almost any environmental changes by the next generation? Could they form 'colonies' or 'hives' and gain communal intelligence?
Your welcome for the suggestion, but kudos for forcing it to make some sense :D
This story keeps sounding better and better!
September 17th, 2006, 06:05 PM
Well, not so much: I envision the Europa lifeforms as being vaguely akin to mollusks and other shellfish in appearance (though much more sparkly :).
Their reprod. itself wouldn't be so amazing, except for the fact that their nuclear material would NEVER unravel into chromatin, or even exist as chromosomes: it is ALWAYS sealed in a SOLID block of crystal in the nucleus and can only be 'read' by voltometry. Therefore the agressive alien cells would never be able to screw with the solid-crystal genome: the DNA-based alien cells could never adapt to this arrangement.