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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?
no subject
but if you only use 2, there's only 16 possible codes, which is not enough. But say you bump it to six: 6^2 is 36, so you could code all the amino acids in two-nucleotide-codons if you had six choices of nucleotide.
Oh! That makes sense. I was thinking about it another way, but that totally works.
And, yeah, Fifth Element is definitely one of those Science Fiction things where I just sit back, enjoy, and try really really really hard to not even think about listening to the science. I'm lucky with Sanctuary in that, since biochemistry/medicine/cell bio isn't my field I can kinda tune the science out.
no subject
There are many things I love about Sanctuary, but they're mostly on the sociocultural end. Science? No. It is magic.
(They forgot to tell Will. Like how they forgot to tell him what their cover story is so he's forever flailing around going "Private... research... facility... no, I'm sorry, I can't tell you what we research... I'm not trying to be dodgy!" Oh, and also: they forgot to tell him "protege" meant "concubine.")
My braintwin wrote me a story about it! Well, specifically about how they failed to tell him it was actually magic. Less so the other bits. Frankly it's funnier to imagine him having several rude awakenings rather than all at once.
no subject
Also, interesting to contemplate: the DNA bases are related to the sources of energy in the cell (triphosphates built on the same bases) which have their tendrils in virtually everything. Downstream, having DNA means maintaining DNA means not only transcribing it, but fixing errors of chemistry or mutation (or otherwise non-complementary bases) and successfully controlling regulatory elements. To say nothing of the changes that would come from the translation aspect of the whole thing...
So if you changed the number of DNA base pairs up from binary to, well, anything, I'd be willing to speculate off hand that there would be major, major changes in the cell from soup to nuts.
no subject
DNA "self repairs," right? How does the repair process know which strand is the incorrect one?