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Okay, for the record: A DNA TRIPLE HELIX MAKES NO SENSE.
Apparently some TV writers need this explanation, and maybe it will magically reach them if I post it here.
A DNA TRIPLE HELIX MAKES NO SENSE.
Right, look, if you are positing a completely alien life form from another planet whose genetic inheritance is not recorded in deoxyribonucleic acid but in some other chemical structure, then sure, run with it, they have triple helices of whatever the hell that chemical is. They also most definitely cannot have babies with humans, do you hear me, really not, but okay, fine, that's a losing battle, whatever, Liam Kincaid.
Let us return to the completely absurd and impossible notion of TRIPLE-STRANDED DNA.
Maybe some basic background on what DNA actually is would help? See, okay, you probably know that there's four bases of DNA that chain together to make the strands, and everyone calls them T, A, C, and G. (They have full names but seriously, even geneticists call them T, A, C, and G, so it's sort of a waste of time or else proof of giant dorkery to know what they are.) What you may not realize is that this is two pairs of complementary bases. T and A bond together, and so do C and G. This means that if on one side of the double helix there is a T base, on the other side there is always an A base. If there is a C base on one side, on the other side there is always a G.
So imagine you have a piece of a strand which says:
TACGCGTAGCCCTTTA
The strand that goes with it to form a double helix HAS to say:
ATGCGCATCGGGAAAT
It cannot say anything else. They have to match. If they don't match, they don't connect. They don't form a double helix.
This is the really key thing I am trying to get at: the two strands of DNA in a double helix do not contain different information. They contain mirror images of the same information. It's like one side is ROT13 of the other side, except there's only four letters in the DNA alphabet, so it's more like ROT2. Why the redundancy? Because the bases have to be reactive enough to chemically copy when the strand is unzipped, but there needs to be some way to put them away and make them stop reacting when it's not time to copy them, and just slapping a mirror version on makes a stable storage form.
Therefore adding a third strand to a DNA helix--in the first place, what the fuck does it hook onto, the complementary bases are already hooked to each other, and in the second place, it wouldn't add new information, because strands just--don't. All the bases in the third strand would have to complement the bases in the first two strands, which means: same goddamn information.
If you are adding genetic material to an existing multi-celled Earth life form as we know them, just splice sequences of regular double helices into existing double helices (aka, either make the strands longer or replace segments of the strands). If it makes you feel really special, add a chromosome or two (be aware: having extra chromosomes is associated with some odd syndromes). Don't add a third strand of DNA to the double helices, it is MEANINGLESS.
If you are imagining a something superspecial and different from existing multi-celled Earth life forms as we know them, and you want, say, more data compressed into less length of strand, or compress more data into the same length of strand (I'm looking at you, Fifth Element), what you would do is add more base pairs. Why? Think binary versus base 10. What's 36 in binary? 100100. Look at how many more digits you need to convey the same concept, because you only have two options to choose from. But if you have ten options, you only need to use two digits, because you're conveying more information per digit. The more base pairs are available to encode information, the more compactly the information can be encoded. This is something I want to see in my scifi, people. The weird alien species with more efficient DNA whose base pairs are TACGEFLM or something. I would even be willing to buy, for the sake of the narrative, the shocking revelation that so-and-so-supposedly-human has a handful of E's and F's, and even some L's and M's in their DNA and so is SECRETLY PART ALIEN.
But not more strands. Just don't. More strands is more copies. More strands is redundancy. More strands is NOT more information. It is not. And when you say it is, in my head I am converting all of your technobabble to "Magic magic, magic magic, magic magic. Sorcery, what ho!"
Glad to get that off my chest.
Is this one of those things where I don't know I'm swimming in water because I was raised by a geneticist?
A DNA TRIPLE HELIX MAKES NO SENSE.
Right, look, if you are positing a completely alien life form from another planet whose genetic inheritance is not recorded in deoxyribonucleic acid but in some other chemical structure, then sure, run with it, they have triple helices of whatever the hell that chemical is. They also most definitely cannot have babies with humans, do you hear me, really not, but okay, fine, that's a losing battle, whatever, Liam Kincaid.
Let us return to the completely absurd and impossible notion of TRIPLE-STRANDED DNA.
Maybe some basic background on what DNA actually is would help? See, okay, you probably know that there's four bases of DNA that chain together to make the strands, and everyone calls them T, A, C, and G. (They have full names but seriously, even geneticists call them T, A, C, and G, so it's sort of a waste of time or else proof of giant dorkery to know what they are.) What you may not realize is that this is two pairs of complementary bases. T and A bond together, and so do C and G. This means that if on one side of the double helix there is a T base, on the other side there is always an A base. If there is a C base on one side, on the other side there is always a G.
So imagine you have a piece of a strand which says:
TACGCGTAGCCCTTTA
The strand that goes with it to form a double helix HAS to say:
ATGCGCATCGGGAAAT
It cannot say anything else. They have to match. If they don't match, they don't connect. They don't form a double helix.
This is the really key thing I am trying to get at: the two strands of DNA in a double helix do not contain different information. They contain mirror images of the same information. It's like one side is ROT13 of the other side, except there's only four letters in the DNA alphabet, so it's more like ROT2. Why the redundancy? Because the bases have to be reactive enough to chemically copy when the strand is unzipped, but there needs to be some way to put them away and make them stop reacting when it's not time to copy them, and just slapping a mirror version on makes a stable storage form.
Therefore adding a third strand to a DNA helix--in the first place, what the fuck does it hook onto, the complementary bases are already hooked to each other, and in the second place, it wouldn't add new information, because strands just--don't. All the bases in the third strand would have to complement the bases in the first two strands, which means: same goddamn information.
If you are adding genetic material to an existing multi-celled Earth life form as we know them, just splice sequences of regular double helices into existing double helices (aka, either make the strands longer or replace segments of the strands). If it makes you feel really special, add a chromosome or two (be aware: having extra chromosomes is associated with some odd syndromes). Don't add a third strand of DNA to the double helices, it is MEANINGLESS.
If you are imagining a something superspecial and different from existing multi-celled Earth life forms as we know them, and you want, say, more data compressed into less length of strand, or compress more data into the same length of strand (I'm looking at you, Fifth Element), what you would do is add more base pairs. Why? Think binary versus base 10. What's 36 in binary? 100100. Look at how many more digits you need to convey the same concept, because you only have two options to choose from. But if you have ten options, you only need to use two digits, because you're conveying more information per digit. The more base pairs are available to encode information, the more compactly the information can be encoded. This is something I want to see in my scifi, people. The weird alien species with more efficient DNA whose base pairs are TACGEFLM or something. I would even be willing to buy, for the sake of the narrative, the shocking revelation that so-and-so-supposedly-human has a handful of E's and F's, and even some L's and M's in their DNA and so is SECRETLY PART ALIEN.
But not more strands. Just don't. More strands is more copies. More strands is redundancy. More strands is NOT more information. It is not. And when you say it is, in my head I am converting all of your technobabble to "Magic magic, magic magic, magic magic. Sorcery, what ho!"
Glad to get that off my chest.
Is this one of those things where I don't know I'm swimming in water because I was raised by a geneticist?
this comment brought to you by a biochemistry prof
So, er, the point is that modified bases already exist and I could totally see evolution just encoding them into tri-phosphates and allowing recognition by polymerases. I could also see interesting unethical lab accidents in which eeeeeeevil scientists somehow incorporate the plethora of modified bases (anything from ratioactive tags to variations on ATCG), available to lab scientists, but that's just me.
You are also totally correct that all the filler, no transcribed stuff could be removed, and with the more efficient use of space you'd have DNA a lot more like mitochondrial DNA, with little extra stuff, but you'd probably have less control over silencing and regulation, and if you really go all mitochondrial on it, you might relax specificity on the wobble base recognition and you'd have reeeeeeally interesting increase mutational rates. Possibly just shortened lifespan stuff, possibly all X-men, but let us not speak of the X-men froonium genetics.
...I'll stop now.
Re: this comment brought to you by a biochemistry prof
If we won't speak of X-Men, about about Goa'uld genetic memory? :P
FROONIUM
We are very delicately balanced, and we rarely waste energy, but when it comes to things like brains and DNA, we have lots of unused space. Maybe it's for future storage needs? Or maybe we just don't know yet what all that extra space is for? (Dun dun duuuuuuuuun......)
*eyebrow*
Re: FROONIUM
Among other things, crap, there was that thing about viruses that have managed to actually embed themselves into DNA? Which evolution responded to by isolating the DNA with non-encoding DNA and turning the whole unit off? So there are diseases that essentially caused those sections of non-encoding DNA getting turned back on and, well, there's a REASON the body turned it off? I saw a really cool and not completely idiotic article on this and I wish I could remember where.
But yeah. I hold with the belief that we don't have massive amounts of unused space in our brains or our DNA, just stuff science hasn't figured out yet. Well, maybe the DNA, a lot of it could just be Nature not doing cleanup after itself after it's turned stuff off, Nature is like that when it's mutating things, but the actively expressed stuff (ie, the BRAIN) is usually pretty tidily efficient. It's not a good survival mechanism to put energy into maintaining a hugely complex oxygen and nutrient intensive organ that's not doing anything with whatever large percentage of itself.
(Er. I'm not a prof or anything, I'm just pre-med with a passion for biology and evolution. I don't claim to be know it that well, just that I do actually have a passable grasp on what the theory of evolution actually is and how mutation works. Which is more than most science fiction can say, cry.)
Re: FROONIUM
Only even the stuff that's sourced from viruses or whatnot which might legitimately be silenced preferably, that can be a source of new advantages in the lateral transmission of proteins and ability.
There's also a whole mess of genes, much like areas of your brain, which are not in use right now, but doesn't mean they aren't *ever*. Like proteins involved in development which are only needed as you grow from a blastocyst to a creature with eyes and nails and a stomach and skin and all that. Just because you don't need to grow new eyeballs now, doesn't mean you probably don't appreciate the genes that helped you make them once upon a time.
Re: FROONIUM
One gene -- one enzyme .... Nope! why?
One gene -- one protein ... Nope! why?
one gene -- one polypeptide ... Nope! why?
so what is a gene? It depends .....
:-D
One wonders what Beadle & Tatum would think!
Re: FROONIUM
Only a small portion of our brain cells are active at a set point in time, but we do need all (or at least most) of them to function.
Now, the younger we are, the more potential there is for the brain to adapt and create workarounds. And new discoveries show that the brain remains changable throughout life, but all of this is through a process of actually USING it, because (as in many cases with the human body) use/need influences function/adaptation.
Re: FROONIUM
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Re: FROONIUM
Re: this comment brought to you by a biochemistry prof
Well, actually, there are. Even really cool ones only being used by a few groups of organisms: http://en.wikipedia.org/wiki/Pyrrolysine
Re: this comment brought to you by a biochemistry prof
Re: this comment brought to you by a biochemistry prof
Oh, and the other rather cool one is this: http://en.wikipedia.org/wiki/Selenocysteine
Re: this comment brought to you by a biochemistry prof
Re: this comment brought to you by a biochemistry prof
Re: this comment brought to you by a biochemistry prof
Re: this comment brought to you by a biochemistry prof