September 12, 2019 0

A New Genetic Alphabet Is Creating Things Nature Has Never Seen


So there are only 4 simple pieces to our genetic
code, right? Cytosine, guanine, adenine, and thymine, C,
G, A, and T. Well, not anymore folks, not anymore. Now…there are six. When you actually think about it, trying to
make an entire complex being and all the crazy stuff that goes with us (gestures at self)
out of only 4 simple pieces isn’t very efficient. The proteins that our DNA codes for are themselves
made out of amino acids, of which there are only 20. Isn’t that crazy? Every living thing is made out of different
combinations of just 20 basic building blocks, coded by just FOUR even more basic building
blocks. So it’s safe to say, scientists have been
dreaming about expanding that toolkit for a long time. That’s right. We’ve upgraded. These ‘unnatural’ additions to genetic
code have names like this and this [point to TOS] but to simplify things we call them
X and Y. And this class of synthetic DNA base pairs
are called xeno nucleic acids, or XNA. Biochemists first started trying to add these
new base pairs to DNA in the 1980s, which as you can imagine, is not easy. Base pair bonding in natural DNA is highly
accurate–A always bonds with T and C always bonds with G, but the pairs we’ve added
are harder to get right. It’s easy for the newbies to mis-pair. This is because the hydrogen bonds that hold
the two sides of the DNA helix together are very weak. And while they’re enough for the natural
stuff, holding synthetically introduced base pairs together properly requires something
a little stronger. One team has gotten around the bonding problem
by making the new base pairs stick together because they’re both hydrophobic, making
them line up properly to bond in an effective way. Others have simply tried to strengthen the
hydrogen bonds by manipulating the structure of the unnatural bases. But that’s really just the first hurdle. Once you’ve gotten the new base pairs to
stick together, you have to make sure they don’t disrupt the rest of the DNA and make
chunks of it nonfunctional. And then you have to get the cells of whatever
organism you’re adding it to to actually accept them and be equipped to produce whatever
these new bases are asking them produce…seems like a pretty big headache. Nature is doing just fine on its own, a master
technician with all its gorgeous cellular machinery–why do we want to mess with it
so much? Well, because it’s worth it. We already genetically engineer organisms
like E. coli to produce a desired chemical product for us, because their genome is easy
to infiltrate and they reproduce so fast you can make industrial quantities of the thing
you want–like insulin, for example. But, as we’ve discussed, we’re only working
with 20 amino acids to build everything out of. Adding in synthetic base pairs could make
it possible for organisms to be able to build proteins out of more unusual materials…like
synthetically produced amino acids. Maybe, metal-binding ones that would be conductive
or magnetic, making bio-materials that could be used in electronics! Ok, ok, but aren’t we getting into mutant
superhero territory, here? It’s easy to wanna make that leap, but we’re
not quite there. Because all of these materials are synthetic–both
the base pairs and any unnatural amino acids those base pairs would code an organism to
use–they are obviously not found in nature. Scientists have to provide these materials
to the organisms in order for the organisms to be able to use them…and in most cases,
even to survive. If the modified organism doesn’t have the
materials to make these synthetic base pairs, they just die. They couldn’t run rogue, Jurassic Park style,
even if they wanted to. Realistically, we’ll use these new capabilities
to produce new catalysts, which are used to improve and speed up chemical experiments. And this could radically transform our ability
to engineer and mass produce more effective medicines. With new DNA and new amino acid building blocks,
we have control over what proteins are produced at a level of detail we could never have previously
imagined. It’s like we’ve been trying to cobble
together shoes by hand, but now we have access to a state of the art shoe-making factory. We just have to figure out the blueprint of
the place, and the high-tech security system. And who knows? Maybe the work that it takes to get us where
we want to go in this field will help us better understand the lingering mysteries of DNA…like
how it all came to together at the beginning of everything to create life. For more on the science-fiction-like reality
of DNA manipulation, check out this video here. And as always, thanks for watching.

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