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.