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DNA – The Instruction Manual for Life · Talking Science

0:00
right now like as you're listening to my voice
0:01
there are two meters of this microscopic uh twisted
0:06
ladder actively unzipping itself inside almost
0:09
every single one of your trillions of cells which
0:12
is wild on its own but but here is the most shocking
0:16
part about this frenetic little construction
0:19
site inside your body. It's the exact same machinery
0:21
everywhere. Exactly. It involves the exact same
0:24
molecular ladder you would find if you, you know,
0:26
zoomed in on the towering eucalypt trees swaying
0:29
outside or the microscopic bacterium invisible
0:31
on your skin or even like a mushroom growing
0:34
on a fallen log. Yeah, which is completely counterintuitive,
0:37
right? Because we look around at this overwhelming,
0:40
just staggering variety of life on Earth. And
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I mean, it feels like common sense to assume
0:45
that that the blueprints for all these wildly
0:47
different living things must be written in, well,
0:50
completely different biological languages. But
0:53
they aren't. No, they really aren't. Every single
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living organism on this planet stores its biological
0:58
instructions in the exact same molecule written
1:01
in the identical chemical alphabet. And that
1:04
brings us to our mission for this deep dive,
1:07
because today we are going to thoroughly unpack
1:10
this molecular manual of life, which is, of course,
1:14
DNA. We're going straight into the physical mechanics
1:16
of it. Like, what is this molecule physically
1:18
made of? The actual architecture. Yeah. How does
1:21
it manage the physics of perfectly copying itself
1:24
without just, you know, snapping in half? How
1:26
does it actually dictate whether you have brown
1:28
eyes or maybe a risk for a certain disease? And
1:31
what is modern science doing now that? We can
1:33
finally read this manual in real time. It's a
1:36
lot of ground to cover. Yeah. But it's so important.
1:39
It is. And I want to say to you, the listener,
1:41
right up front. This isn't just some abstract
1:44
textbook theory we're talking about today. This
1:46
is the story of the literal biological machinery
1:50
that is keeping you alive, maintaining your tissues,
1:52
and dictating your biological reality right at
1:55
this very second. Yeah, grounding it in our own
1:57
bodies is honestly the best way to understand
1:59
it. Because when we fully grasp the mechanics
2:01
of what is happening inside our own cells, we
2:04
simultaneously unlock the biggest picture possible.
2:07
The universal picture. Exactly. The universality
2:10
of DNA. I mean, the fact that you... and that
2:12
mushroom and that eucalypt tree all operate on
2:15
the exact same molecular code. It's the most
2:17
profound, undeniable piece of evidence we have
2:20
that everything alive today descends from a single
2:24
common ancestor. Because the odds of it happening
2:26
twice are... Basically zero. The statistical
2:30
probability of this highly specific, incredibly
2:33
complex chemical alphabet evolving independently
2:36
multiple times in the exact same way is effectively
2:39
zero. So you're looking at a shared heritage.
2:42
OK, so if we share this underlying operating
2:44
system with the rest of the natural world, I
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mean, we really need to know how it actually
2:47
works. Let's zoom all the way down past the organs,
2:50
past the tissues, you know, down into a single
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microscopic cell and into the nucleus right at
2:55
its center. What are we physically looking at
2:57
here? What is the actual architecture of life?
3:00
Well, let's start by just demystifying the name
3:02
itself, because the name tells you exactly how
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it's built. DNA stands for deoxyribonucleic acid.
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Deoxyribonucleic acid. It's a mouthful. It is,
3:10
but we can break that down. Deoxyribose. That
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refers to the specific type of sugar molecule
3:16
that forms the foundation of its structure. Wait,
3:19
sugar? Like actual sugar? Chemically speaking,
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yes. A type of sugar. Then the nucleic part simply
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tells us where we usually find it. It's safely
3:27
housed inside the nucleus of the cell. Okay,
3:30
sugar in the nucleus. And the acid part. The
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acid refers to the fact that under normal cellular
3:36
conditions, the molecule has a tendency to give
3:38
up a proton, which makes it chemically acidic.
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So if we put it all together, we basically have
3:43
an acidic sugar molecule sitting in the nucleus.
3:46
Essentially, yes. But the shape of it is what
3:48
everyone really recognizes, right? The double
3:50
helix, that famous twisted ladder. But I really
3:54
want to push on that for a second. Why is it
3:57
twisted? Because we always draw it as a spiral,
4:00
but molecules don't just choose a shape to look
4:03
elegant for a textbook cover. There has to be
4:06
a physical, chemical reason it twists like that.
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Oh, there absolutely is. The twist is entirely
4:11
driven by the thermodynamics of the cell environment.
4:13
Thermodynamics. Yeah. To understand that, we
4:15
have to look at the latter's two main components.
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You have the side rails and the rungs. So the
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two long side rails, the parts you would hold
4:21
if you were actually climbing it. Right. They're
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made as an alternating pattern. of that deoxyrobo
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sugar and a phosphate molecule. We call this
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the sugar -phosphate backbone. Okay, so it's
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just sugar, phosphate, sugar, phosphate, millions
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of times over. Exactly. And crucially, this backbone
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carries a negative electrical charge, and it
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is hydrophilic. Meaning it loves water. Right.
4:45
It readily interacts with the water that fills
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the cell. But the rungs of the ladder, however,
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the steps, are made of completely different molecules
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called bases. And these bases are hydrophobic.
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They strongly repel water. Oh, wow. Okay, so
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you have a molecule where the outside edge desperately
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wants to be in water and the inside rungs desperately
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hate water and the whole thing is suspended in
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a cell that is basically mostly water. You've
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hit the exact physical dilemma. The molecule
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naturally wants to minimize its energy state.
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So the water -loving backbone forms this protective
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outer shield and the water -repelling bases stack
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up on the inside to hide from the water. Like
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huddling together for warmth. Yeah, exactly.
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But here's the catch. Because of the specific
5:27
angles of the chemical bonds between the sugar
5:30
and those bases, The only physical way for those
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bases to stack tightly enough to completely lock
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out the water is if the entire structure twists
5:39
into a spiral. No way. So the cell's watery environment
5:42
literally forces the latter into that iconic
5:45
double helix shape. It does. The environment
5:47
squeezes it into a spiral staircase. That makes
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so much more sense than just assuming it's some
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random arbitrary design. It's a thermodynamic
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inevitability. Okay, so this sugar phosphate
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backbone is essentially structural scaffolding.
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It gives the molecule a shape and stability.
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It protects the inside from water. But it isn't
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the actual information, right? It's just the
6:05
physical track holding the data. Yes. Think of
6:08
it like a highly advanced, ultra -durable magnetic
6:11
tape. Like an old VHS or cassette tape? Yeah,
6:14
perfect. The plastic casing of the tape is absolutely
6:17
vital for protecting the data from degrading.
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But you don't read the plastic casing to watch
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the movie. You read the magnetic variations on
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the inside tape. In DNA... The information in
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the movie is written entirely in those hydrophobic
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rungs hidden away in the center of the helix.
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And those rungs are where we encounter the alphabet.
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Because each rung is made of two chemical units
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that meet in the middle, right? These are the
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bases. And I feel like here is where the sheer
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simplicity of this system becomes almost hard
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to believe. It really is. Because there are only
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four bases in this entire system. Just four.
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Adenine, thymine, guanine, and cytosine. Which
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are usually just abbreviated to A, T, G, and
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C. Right. A, T, G, C. Four letters. I mean, we
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use an alphabet of 26 letters to write a simple
6:59
email. And even then, we struggle to articulate
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complex ideas sometimes. But nature uses precisely
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four chemical letters to write the instructions
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for, like the human brain or the bioluminescence
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of a firefly, the venom of a cobra, the bark
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of a tree, everything. It all comes down to just
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the sequence of those four letters along the
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immense length of that twisted ladder. It's an
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absolute masterclass in efficiency. But... You
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know, it poses a massive mechanical problem.
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What do you mean? Well, if this fragile, twisted
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ladder holds the complete memory of a species,
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how does it physically copy itself without losing
7:35
information? I mean, when a cell divides to make
7:38
a new cell, which is happening literally millions
7:40
of times a second in our bodies, how does it
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duplicate billions of letters perfectly? Right,
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because if you gave me a book with three billion
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letters in it and told me to hand copy it, I
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would make thousands of typos, probably on the
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first page. How does a mindless chemical structure
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avoid losing the plot? The answer to that lies
7:58
in the single most important structural rule
8:00
of DNA. This rule dictates exactly how those
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four letters interact with each other to form
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the rungs, because they don't just pair up randomly.
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There is a strict physical pairing rule. A always
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pairs with T, and G always pairs with C. A to
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T, G to C. Okay, but again, I have to ask why.
8:18
Because we can't just memorize the rule for this
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deep dive, we need to know the mechanism. Why
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can't an A pair with a G? It comes down to their
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physical size and their chemical bonding points.
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So the four bases belong to two different chemical
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families. A and G are larger molecules. They
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have this double ring structure and we call them
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purines. T and C are smaller, single ring molecules
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called pyrimidines. So one is wide and one is
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narrow? Yes. Now remember the two rails of the
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DNA backbone, they are kept at a perfectly uniform
8:46
distance apart all the way down. If two large
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bases like an A and a G tried to pair together,
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the rung would be too wide and would visibly
8:54
bulge the ladder outward. Like a warped step
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on a staircase. Exactly. And if two small bases
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paired, the rung would be too short and the latter
9:01
would pinch inward. So to keep the distance perfectly
9:04
uniform, every single rung must consist of one
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large base and one small base. Okay, so that
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explains why a large A has to pair with a small
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T or C, but why specifically T, why not C? Because
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they're both small, right? They are, but that
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specific pairing is dictated by hydrogen bonds.
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Think of hydrogen bonds like molecular Velcro.
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Adenine and thymine are chemically shaped so
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that they form exactly two hydrogen bonds with
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each other. Guanine and cytosine are shaped to
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form exactly three hydrogen bonds. So that's
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a lock and key mechanism. It really is. So A
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and T are like a two -prong electrical plug and
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a two -prong outlet. And G and C are a three
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-prong plug and a three -prong outlet. And A
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physically cannot bond with the C because the
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prongs just don't line up. Precisely. The physics
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of the molecules makes it impossible for them
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to pair incorrectly without causing severe physical
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distortion. And if that happens, the cell's proofreading
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machinery would immediately recognize it as an
10:00
error and try to fix it. But this strict two
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-prong, three -prong pairing rule, ATGC, provides
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the ultimate built -in backup system. How so?
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Because if you know the sequence of letters on
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one side of the ladder, you inherently know the
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exact sequence on the opposing side. Let's visualize
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that for the listener. So if I'm reading down
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one half of the ladder, right, just the left
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rail, and I see the sequence A, G, G, C, I know
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with mathematical certainty what is on the other
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side. You do. Because an A requires a T, A, G
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requires a C. So an AGTTC strand simply must
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be locked into a TCC AG strand on the other side.
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The molecule essentially carries a mirrored backup
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copy of itself. at all times. Yeah. And that
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mirroring that specific realization was the foundational
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breakthrough made in 1953 by James Watson and
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Francis Crick. Though it is extremely crucial
10:48
to note here that their model was heavily dependent
10:50
on X -ray crystallography data. Right. The famous
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photo 51. Yes. Produced by Rosalind Franklin.
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Her X -ray data proved the physical dimensions
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of the helix. And knowing the exact width of
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the helix is what allowed Watson and Crick to
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realize that the bases had to pair in this specific
11:09
ATGC manner to fit inside. And when they finally
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published their paper on this, they included
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what has to be just the most understated sentence
11:18
in scientific history. Oh, I know the one you
11:20
mean. Right. They casually wrote that. This specific
11:23
pairing, and I'm quoting here, immediately suggests
11:26
a possible copying mechanism for the genetic
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material. Like they essentially found the mechanical
11:30
secret to all biological reproduction and just
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casually floated it as a possible mechanism at
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the end of the paper. Well, they understood the
11:37
gravity of it perfectly. They knew that if the
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two strands complement each other perfectly,
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like a mirror, you have a literal, physical way
11:45
to replicate the entire molecule. So let's talk
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through that replication process. Because we
11:51
often hear the analogy of a zipper on a jacket.
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You pull the zipper straight down the middle,
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separating the two halves. The teeth pulling
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apart are those hydrogen bonds, you know, the
12:00
two prong and three prong connections we just
12:02
talked about breaking. So you end up with two
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separate strands with all those half rungs exposed.
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It's a great visual. But let's look at the actual
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molecular machinery doing the unzipping because
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it doesn't just pull apart on its own by magic.
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An enzyme. which is a specialized protein worker
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called Helicase. acts as the zipper pull. Helicase.
12:22
Right. Helicase physically wedges itself between
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the two strands and just plows forward, breaking
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the hydrogen bonds at a staggering rate of up
12:31
to a thousand base pairs per second. Wait, a
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thousand per second? Up to a thousand, yes. But
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wait, if you have a piece of string that is tightly
12:38
twisted into a spiral and you violently pull
12:40
the two strands apart in the middle, the twisting
12:43
tension gets pushed further down the string.
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Like if you've ever played with the twisted yarn,
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it gets tighter and tighter until the string
12:48
just snarls into a knot. or snaps entirely. Yes.
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And DNA faces that exact physical threat. If
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helicase just kept unwinding at that speed, the
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tension ahead of the split would physically shatter
13:00
the DNA backbone. The molecule would be destroyed.
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So how does it survive its own unzipping? The
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cell deploys another enzyme called tupisomerase.
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Tupoisomerase. Yes. This enzyme travels ahead
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of the enzaving helicase. It temporarily snips
13:16
the DNA backbone, literally cutting it, letting
13:19
the tension spin out and relax, and then taping
13:21
it back together in a fraction of a second. That
13:24
is insane. So we basically have a demolition
13:26
crew plowing through the center of the building
13:28
and an engineer running ahead to temporarily
13:29
cut the structural beams to relieve the tension
13:32
so the whole building doesn't collapse on itself.
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That's a fantastic way to picture it. And once
13:37
those strands are safely separated by helicase,
13:39
they're exposed to the interior fluid of the
13:41
nucleus. And that fluid is just flooded with
13:44
free -floating individual bases, leucates, Ts,
13:48
Gs, and Cs drifting around. This is where a third
13:51
enzyme called DNA polymerase comes in. builder
13:53
enzyme. The builder. So DNA polymerase travels
13:57
along the exposed single strand. And thanks to
14:00
our strict pairing rule, it doesn't even have
14:02
to, like, think about what to build. If it encounters
14:06
an exposed A on the original strand, the physical
14:09
shape of that A will only allow a free -floating
14:11
T to click into place. Because of the hydrogen
14:14
bonds, the two -prong plug automatically finds
14:17
the two -prong outlet. So as the builder moves
14:19
down the separated strands, it just pulls these
14:22
loose pieces out of the cellular soup and locks
14:24
them in. And because it's happening on both of
14:26
the separated halves simultaneously, you end
14:28
up... up with two complete double helixes. Where
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there was originally one double helix, there
14:33
are now two perfectly identical copies. And notice
14:36
the elegance of the system. Each of the new double
14:38
helices consists of one original parent strand
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and one freshly built daughter strand. Half is
14:44
conserved from the original and half is brand
14:46
new. Which guarantees that the information is
14:48
perfectly preserved through generations and generations
14:51
of cell division. And to ground this again for
14:54
you listening right now, This orchestrated chaos,
14:58
you know, the helicase plowing, the poison rays
15:01
snipping, the polymerase building at a thousand
15:03
letters a second is happening inside you right
15:06
now. Right. It's very second. If you are like
15:08
recovering from a workout or fighting off a cold
15:11
or honestly just maintaining the lining of your
15:13
stomach, your body is executing this exact copying
15:16
mechanism on billions of cells as you listen
15:19
to this. Which naturally leads us to a pretty
15:22
staggering logistical issue regarding physical
15:24
space. Oh, absolutely. Absolutely. Because if
15:26
we have billions of cells constantly doing this
15:28
unzipping and copying, the sheer volume of this
15:31
physical material must be absolutely enormous.
15:34
I mean, how much DNA is actually inside us? Well,
15:36
let's isolate just one single microscopic human
15:39
cell first. If you were to extract the DNA from
15:42
the nucleus of one human cell and stretch it
15:45
out into a single straight line, it would measure
15:47
roughly two meters long. Two meters, over six
15:50
feet of DNA inside one single completely invisible
15:53
cell. Yes. And the compartment it lives in, the
15:56
nucleus, it's only about six micrometers across.
15:59
That is a few thousands of a millimeter. The
16:01
geometry of that feels impossible. Like I'm trying
16:03
to picture that. And if you scale that up, that's
16:05
like trying to pack 24 miles of extremely fine
16:08
fishing line into a single tennis ball. How does
16:11
the cell prevent this massive thread from just
16:13
becoming a hopelessly tangled knot? Because if
16:16
it tangles, the helicase can't unzip it, right?
16:19
The cell can't divide and the organism dies.
16:21
Exactly. The solution is an incredibly sophisticated
16:23
packing mechanism. The cell doesn't just stuff
16:26
the DNA inside randomly. It actively spools it.
16:29
The long thread of the double helix wraps tightly
16:32
around clusters of specialized proteins called
16:35
histones. Histones. And I remember reading they
16:38
are positively charged, right? Why is that important?
16:41
Well, remember how we established earlier that
16:43
the sugar phosphate backbone of the DNA has a
16:45
negative charge? Oh. Opposite charges attract.
16:48
The negative DNA physically snaps onto the positive
16:51
histone proteins like magnets. It's an electrostatic
16:54
hold. Exactly. It's a very tight grip. The DNA
16:58
wraps around a cluster of eight histones, creating
17:00
a structure called a nucleosome. If you looked
17:03
at it under a powerful electron microscope at
17:05
this specific stage, it looks exactly like beads
17:08
on a string. Okay, beads on a string, but that's
17:10
still pretty long. It is, so it doesn't stop
17:12
there. Those beaded strings then coil up into
17:15
a thicker fiber, and that fiber then supercoils,
17:18
literally looping and folding back on itself
17:21
again and again and again to create highly...
17:24
dense, highly organized structures. Chromosomes.
17:27
Yes. A chromosome is simply this two meter long
17:29
thread of DNA wound around millions of these
17:32
microscopic magnetic schools and coiled upon
17:35
itself until it is dense enough to be moved around
17:37
during cell division without tangling. And humans
17:39
package our two meters of DNA into 46 distinct
17:42
chromosomes, which come in 23 pairs. You inherit
17:45
23 from your biological mother and 23 from your
17:47
biological father. I want to run a quick thought
17:49
experiment here to really hammer home the scale
17:51
of this natural engineering for anyone listening.
17:53
We know one single cell contains two meters of
17:56
DNA and an average adult human body contains
17:58
roughly 30 trillion cells. That's the generally
18:02
accepted estimate. Yes. Yeah. Give or take a
18:04
few trillion. Right. So if you somehow managed
18:06
to magically extract the DNA from every single
18:09
cell in your own body, uncoiled it from all those
18:12
magnetic histone spools and laid every single
18:15
strand end to end in a straight line. How far
18:19
would that physical thread reach? The math requires
18:22
astronomical distances. I mean, it wouldn't just
18:25
stretch across the planet. If you laid all the
18:27
DNA in your body end to end, it would stretch
18:29
from the Earth to the sun and back again. Roughly
18:32
60 times. From the Earth to the Sun, over 90
18:34
million miles, and back, dozens of times. All
18:38
of that is physically packed inside the boundaries
18:40
of your skin. It is a profound demonstration
18:42
of how incredibly thin the DNA molecule actually
18:45
is, and how brilliantly the cell manages to organize
18:48
its physical environment. It is genuinely awe
18:50
-inspiring. So we now understand the architecture.
18:54
We know it's a twisted ladder made of four letters,
18:57
locked together by hydrogen bonds, spooled around
18:59
charged proteins, and we know how it unzips to
19:02
perfectly copy itself. But, you know, an instruction
19:06
manual is completely useless unless someone is
19:08
actually reading it to build something. What
19:10
is this code actually doing all day to keep us
19:13
alive? Now we move from the structure of DNA
19:15
to its active function. The primary job of most
19:19
functional DNA sequences is to specify the creation
19:22
of proteins. And we really need to clarify what
19:24
we mean by protein because the everyday use of
19:26
that word usually refers to, like, dietary nutrition.
19:29
We think of a chicken breast or protein shakes
19:31
at the gym. Right. Dietary protein is what we
19:33
consume to get raw materials. But in molecular
19:36
biology, proteins are the actual machinery of
19:39
life. They are the physical agents that do all
19:41
the work inside your cells. So if a human cell
19:43
is a bustling factory, the proteins aren't just
19:45
the raw materials sitting on pallets. The proteins
19:48
are the assembly line workers, the conveyor belts,
19:51
the support beams holding up the roof, and the
19:53
security guards checking IDs at the door. That
19:56
is a perfect analogy. Proteins are incredibly
19:59
diverse. They are the enzymes that physically
20:01
break down your food in your stomach. They form
20:04
the structural fibers that give your body its
20:06
physical shape, like the collagen holding your
20:08
skin together and the keratin making up your
20:10
hair and nails. They are the signaling molecules
20:13
too, right? Yes. Hormones like insulin are actually
20:16
proteins that travel through your blood to tell
20:18
cells to absorb sugar. Antibodies are highly
20:22
specialized proteins that your immune system
20:23
deploys to physically bind to and neutralize
20:26
invading viruses. Hemoglobin is a protein complex
20:30
inside your red blood cells, shaped specifically
20:32
to trap oxygen in the lungs and release it in
20:35
the tissues. Truly, every single biological action
20:38
is carried out by a protein. So the DNA isn't
20:40
doing the work itself. The DNA is just the master
20:43
blueprint sitting safely in the nucleus manager's
20:45
office, dictating exactly how to build every
20:47
single protein worker in the factory. Precisely.
20:50
But this creates a huge logistical barrier for
20:53
the cell. The DNA is far too precious, and honestly,
20:56
too enormous, to ever leave the protective vault
20:59
of the nucleus. If it goes out onto the messy,
21:02
highly active factory floor of the main cell,
21:04
it could easily be damaged or destroyed. So the
21:07
cell uses a two -step communication system to
21:10
get the instructions out safely. It's kind of
21:12
like having a priceless ancient reference text
21:15
in a restricted library. You definitely can't
21:17
take the book out to the workshop where there's
21:19
grease and sparks. So step one has to be making
21:22
a copy of just the specific page you need. Exactly.
21:25
We call step one transcription. When the cell
21:27
needs to build a specific protein, say, it needs
21:29
more insulin, an enzyme goes into the nucleus,
21:32
locates the specific sequence of DNA containing
21:34
the insulin recipe, unzips just that tiny section,
21:38
and creates a working copy. But it doesn't make
21:40
a DNA copy, does it? No, it transcribes the information
21:43
into a slightly different, closely related molecule
21:46
called messenger RNA or mRNA. Oh, mRNA, a term
21:50
that became globally recognized during the development
21:52
of the COVID -19 vaccines. How is RNA physically
21:55
different from DNA? Chemically, it uses a slightly
21:58
different sugar for its backbone ribose instead
22:01
of deoxyribose. And instead of the base thymine,
22:04
the T, RNA uses a base called uracil or U. Structurally,
22:09
it is normally just a single strand, not a double
22:12
helix. Why the change in materials? Why not just
22:15
use the exact same letters and make a mini DNA
22:17
strand? Because mRNA is inherently designed to
22:20
be temporary. The cell doesn't want the factory
22:23
floor permanently cluttered with old instructions.
22:26
The chemical structure of RNA makes it far less
22:28
stable than DNA. It degrades relatively quickly.
22:31
It exists just long enough to deliver the message
22:33
to the factory, and then it breaks down so the
22:36
components can be recycled. So we have transcribed
22:38
our temporary mRNA copy, and because it's small
22:41
and totally expendable, it is allowed to exit
22:43
the nucleus vault and travel out into the main
22:45
body of the cell. What is step two? Step two
22:48
is translation. The nucleotide language of the
22:50
mRNA needs to be literally translated into the
22:52
amino acid language of proteins. This translation
22:54
is performed by a massive, complex molecular
22:57
machine called a ribosome. So the ribosome is
22:59
the foreman on the factory floor reading the
23:02
blueprint page. How does it physically read those
23:04
chemical letters? The ribosome basically clamps
23:07
around the mRNA strand and begins reading the
23:09
sequence, but it doesn't read one letter at a
23:12
time. It reads the letters in discrete groups
23:14
of three. Each three -letter sequence is called
23:17
a codon. Okay, so if the mRNA sequence is AUGCCA,
23:21
the ribosome reads AUG as one distinct word and
23:25
CCA as the next distinct word. Exactly. And the
23:28
magic of the genetic code is that each specific
23:31
three -letter codon corresponds to exactly one
23:34
amino acid. And amino acids are the physical
23:37
building blocks that make up a protein. Yes.
23:39
Think of amino acids like biological Lego bricks.
23:41
Life on Earth utilizes 20 different types of
23:44
these amino acids. As the ribosome reads the
23:46
MRA, another molecule called transfer RNA, or
23:49
tRNA, floats by. One end of the tRNA perfectly
23:53
matches the three -letter codon being read, and
23:55
the other end carries the specific amino acid
23:57
that codon asks for. So the tRNA is a delivery
23:59
driver. It absolutely is. The ribosome reads
24:02
the AUG codon, the corresponding tRNA delivery
24:06
driver docks into place, and the ribosome clicks
24:09
that amino acid onto the chain. Then the ribosome
24:12
moves forward exactly three letters, reads the
24:14
next codon, the next delivery driver arrives,
24:17
and the ribosome clicks the new amino acid onto
24:19
the first one. This builds a long physical chain
24:22
of amino acids assembled in the precise order
24:25
originally dictated by the DNA back in the nucleus.
24:28
And once the ribosome reaches a specific stop
24:30
codon, it releases the chain. Now, because of
24:34
the distinct chemical properties of the different
24:36
amino acids in the chain, some love water, some
24:38
hate it, some have positive charges, some have
24:40
negative charges, the long chain instantly folds
24:42
up on itself into a highly specific, complex
24:44
3D shape. And that folded shape is the functional
24:48
protein ready to do its job. Form dictates function.
24:51
The sequence dictates the folding, and the folding
24:54
dictates what the protein can actually do. But
24:56
let's pause and look at the mathematical logic
24:59
of this three -letter codon system for a second,
25:01
because there is an incredible protective mechanism
25:03
hidden in the math here. We have an alphabet
25:06
of four letters, and they are read in groups
25:08
of three. If you multiply that out four times
25:11
four times four, there are exactly 64 possible
25:15
combinations. Correct. 64 possible three -letter
25:19
words. But you just said the factory only uses
25:21
20 amino acid Lego bricks. If there are 64 words
25:25
but only 20 actual ingredients to ask for, what
25:27
are the other 44 words doing? They provide redundancy.
25:30
Because there are 64 words and only 20 amino
25:33
acids, most amino acids are coded for by multiple
25:36
different codons. For example, the amino acid
25:38
proline is requested by the codons CCU, CCC,
25:41
CCA, and CCG. Any of those four sequences tells
25:45
the ribosome, put a proline here. There are chemical
25:48
synonyms, multiple ways to say the exact same
25:50
thing. Exactly. The genetic code is highly degenerate,
25:52
meaning there is built -in redundancy, particularly
25:54
in the third letter of the codon. And this redundancy
25:57
is an evolutionary shield against chaos, which
26:00
brings us perfectly into what happens when the
26:01
system actually makes a mistake. Right, glitches
26:04
in the matrix. Because if helicase and polymerase
26:06
are rushing along, unzipping and copying billions
26:09
of letters at lightning speed, mistakes are physically
26:12
inevitable. What is a mutation, fundamentally?
26:15
Stripped of all the science fiction tropes from
26:17
movies, a mutation is simply a change in the
26:20
DNA sequence, a chemical typo. An A accidentally
26:24
gets copied as a G, or maybe a letter gets skipped
26:26
entirely. How does that happen, though, beyond
26:28
just polymerase making a sloppy typo during replication?
26:32
Well, the environment constantly damages our
26:34
DNA. Ultraviolet light from the sun is a major
26:37
culprit. When UV photons hit your skin cells,
26:40
the physical energy can cause two adjacent thymine
26:43
bases, two Ts on the DNA strand, to physically
26:46
fuse together into a knot called a thymine dimer,
26:49
which the copying machinery really struggles
26:51
to read. Wow. Yeah. And certain chemicals, radiation,
26:54
and even the normal metabolic byproducts. of
26:56
simply converting your food to energy can physically
26:59
alter the DNA structure inside your cells. And
27:01
when the copying machine hits that damage, it
27:03
basically has to guess the letter, and a mutation
27:06
is cemented into the code. Now, the cultural
27:08
perception of a mutation is that it is inherently
27:10
monstrous. It causes disease or radiation sickness
27:14
or turns you into a superhero. But that's where
27:16
the redundancy of the 64 codons comes in to save
27:19
us, right? Exactly. A huge percentage of point
27:22
mutations, which is where a single letter is
27:24
swapped, are entirely silent. Let's go back to
27:26
our proline example. The original DNA says CCA,
27:29
so the ribosome clicks a proline onto the chain.
27:32
If a UV falcon damages that DNA, and during repair,
27:35
it mutates, so the sequence now reads CCG. CCG
27:40
is a synonym. It still codes for proline. Precisely.
27:43
The ribosome reads the mutated sequence, but
27:46
the tRNA delivery driver still brings a proline.
27:48
The resulting amino acid chain is 100 % identical.
27:51
The protein folds the exact same way and it functions
27:53
perfectly. The mutation occurred, but it was
27:55
physically meaningless. Furthermore, massive
27:58
stretches of our DNA do not code for proteins
28:00
at all. If a typo lands in certain non -coding
28:02
regions, it often has absolutely no effect on
28:04
the factory floor. It's like a typo occurring
28:07
in the blank margins of the manual. Nobody really
28:09
cares. But we can't pretend all typos are harmless.
28:13
When a typo occurs in a critical area, the physical
28:16
consequences can be absolutely devastating. It
28:19
certainly can. If a single letter change occurs
28:22
early in a critical gene, it might specify a
28:25
completely different amino acid. If you swap
28:27
a water -loving amino acid for a water -hating
28:30
one, the entire long chain will fold incorrectly.
28:33
And a misfolded protein is usually a completely
28:35
broken machine. Our source material gives a stark,
28:38
really powerful example of this, sickle cell
28:41
disease. Walk us through the physical mechanics
28:43
of that single typo. Right. So sickle cell disease
28:45
is caused by a mutation in the gene that builds
28:48
hemoglobin, which is the oxygen -carrying protein
28:51
in your red blood cells. The original healthy
28:53
sequence contains a codon that asks for an amino
28:56
acid called glutamic acid, which is hydrophilic.
28:59
It likes water. Okay, so it helps the hemoglobin
29:02
dissolve nicely in the fluid of the blood cell.
29:04
Exactly. But in sickle cell, a single DNA letter
29:07
is swapped. Just one. An A is replaced by a T.
29:11
That single chain shifts the codon so that it
29:13
now asks for valine instead of glutamic acid.
29:16
And valine is hydrophobic. It strongly hates
29:19
water. Oh, no. So suddenly on the outside of
29:22
this protein, there is a physical patch that
29:24
is desperately trying to hide from the watery
29:27
environment of the cell. Yes. And the only way
29:29
the valine patch can hide from the water is by
29:32
sticking to a hydrophobic valine patch on another
29:34
mutated hemoglobin molecule nearby. The proteins
29:38
begin to click together, forming long, rigid
29:41
physical chains inside the red blood cell. These
29:44
rigid chains stretch the cell out of its normal,
29:46
flexible, round shape into a stiff, curved sickle
29:49
shape. And those stiff, sickle -shaped cells
29:52
get physically stuck in the tiny capillaries
29:54
of the blood vessels, causing severe pain and
29:56
organ damage. All because one single A became
29:59
a T, causing one water -loving building block
30:01
to be swapped for a water -hating one. It perfectly
30:04
illustrates how incredibly sensitive the physical
30:07
realities of our bodies are to the molecular
30:09
realities of our DNA. But this introduces a really
30:12
profound philosophical and biological paradox.
30:16
We are talking about these mutations, these typos,
30:19
as the mechanism of devastating life -altering
30:22
diseases. Yet these exact same copying errors
30:26
are simultaneously the reason we exist at all.
30:29
That is the ultimate dual nature of DNA. While
30:32
most mutations are silent, and some are disastrously
30:35
harmful, a tiny, tiny fraction of mutations happen
30:39
to alter a protein in a way that provides a physical
30:42
advantage in a specific environment. A typo that
30:44
actually improves the machine. Right. A mutation
30:47
might slightly alter the shape of an enzyme,
30:49
so it breaks down a new type of food source more
30:51
efficiently. Or it might alter a pigment protein,
30:53
providing better camouflage against predators.
30:55
If that advantageous mutation helps the organism
30:58
survive and reproduce, that specific typo gets
31:00
passed on to the next generation. This is natural
31:02
selection in action. It is the raw physical material
31:06
of evolution. Natural selection is simply a filter.
31:09
It can only select from the variations that exist
31:11
in front of it. And mutation is the solitary
31:14
source of that new variation. If DNA polymerase
31:18
never made a typo, if DNA was perfectly rigidly
31:21
immune to environmental damage, life would be
31:23
a stagnant loop. we would still be identical
31:26
single -celled organisms in the ocean. So the
31:28
engine of genetic disease is the exact same mechanism
31:31
as the engine of evolutionary diversity. Without
31:34
the vulnerability that causes sickle cell or
31:36
cancer, we wouldn't have the adaptability that
31:39
gave us the human brain or the wings of an eagle
31:41
or the bark on that tree. They are completely
31:43
inseparable realities of the exact same chemical
31:46
mechanism. Man, that's heavy. I want to shift
31:49
our focus now to how we actively talk about this
31:52
code in our everyday lives. Because out in the
31:54
world, people rarely talk about nucleotides or
31:56
codons. We talk about genes. And this is an area
31:59
where popular language causes massive misunderstandings
32:02
about how our biology actually works. Oh, definitely.
32:04
The word gene carries a lot of cultural baggage.
32:07
In molecular biology, a gene is generally defined
32:10
as a specific sequence of DNA that contains the
32:13
complete instructions to transcribe an RNA molecule,
32:16
usually to build a specific protein. So a gene
32:19
is essentially one complete, discrete recipe
32:22
in the larger cookbook. That is a highly functional
32:25
way to think about it. And understanding how
32:27
many recipes we have leads to one of the most
32:29
humbling discoveries in modern science. In the
32:31
1990s and early 2000s, when the International
32:34
Human Genome Project was working to sequence
32:36
human DNA for the first time, literally reading
32:39
all three billion letters, there was intense
32:42
speculation about how many genes we would actually
32:44
find. Which makes sense. I mean, humans are staggeringly
32:47
complex. We have intricate immune systems. We
32:49
have the cerebral cortex. We build civilizations.
32:51
The assumption was that our cookbook must be
32:53
incredibly sick. The prevailing estimates guessed
32:56
humans had around 100 ,000 to maybe 150 ,000
32:59
distinct genes. But when the sequencing was completed,
33:02
the actual number revealed what became known
33:04
as the roundworm dilemma. Lay the numbers on
33:07
us. Prepare to humble everyone listening. It
33:09
turns out humans possess roughly 20 ,000 protein
33:13
-coding genes. Only 20 ,000. Yes. To put that
33:16
in perspective, a microscopic transparent soil
33:19
nematode, a tiny roundworm called C. elegans,
33:22
which consists of exactly 959 cells total, has
33:26
about 20 ,000 genes as well. I think anyone listening
33:29
right now is completely justified in feeling
33:31
a little insulted by that. How is it physically
33:34
possible that a complex human being with a brain
33:36
capable of understanding its own existence operates
33:39
on the exact same number of instruction manuals
33:42
as a microscopic worm living in the dirt? It
33:44
forces us to realize that biological complexity
33:47
is not simply a matter of gene count. It's not
33:49
about how many recipes you own. It's about the
33:51
sophistication of how and when you cook them.
33:53
The answer to human complexity lies in gene expression
33:57
and regulation. Meaning just because you possess
33:59
a gene doesn't mean the factory is actually using
34:01
it right now. Precisely. Let's look at your own
34:04
body again. Almost every single one of your 30
34:07
trillion cells contains the exact same 2 meters
34:10
of DNA. The vault in your liver cell contains
34:13
the exact same 20 ,000 genes as the vault in
34:16
a neuron in your brain. Yet a liver cell is a
34:20
blocky chemical filter processing toxins, and
34:23
a neuron is a long, spindly wire firing electrical
34:25
impulses. They look and behave like they belong
34:29
to completely different species. How do they
34:31
differentiate if they have the same manual? Because
34:34
of regulation. In the liver cell, the genes responsible
34:37
for building neural pathways are heavily repressed.
34:40
They're physically locked down and switched off.
34:41
The genes for processing toxins are wide open
34:44
and highly active. In the neuron, the exact opposite
34:47
is true. The complexity comes from the dynamic
34:50
network of turning genes on, turning them off,
34:52
or dialing them up and down like a dimmer switch.
34:54
How does the cell physically flip these switches?
34:56
You mentioned earlier that huge portions of our
34:59
DNA do not code for proteins. For a long time,
35:01
the public was taught that this was just junk
35:03
DNA. Junk DNA is a term that biologists deeply,
35:07
deeply regret. It was coined simply because we
35:09
didn't initially understand what it did as it
35:12
didn't code for proteins. But we now know that
35:15
this massive expanse of non -coding DNA is actually
35:18
the control room. It's the regulatory network.
35:20
Yes. These non -coding regions contain sequences
35:23
called promoters and enhancers. They act as physical
35:26
landing pads for specialized proteins called
35:28
transcription factors. When a transcription factor
35:31
binds to an enhancer region, it physically bends
35:33
the DNA strand, bringing it into contact with
35:36
a specific gene to initiate transcription. Furthermore,
35:39
we have a whole layer of physical control called
35:41
epigenetics. Epigenetics. The physical modification
35:44
of the DNA structure itself without changing
35:46
the actual letters. Exactly. The cell can attach
35:49
a small chemical tag, a methyl group, directly
35:51
to the cytosine bases in the DNA. These methyl
35:55
tags physically prevent the transcription machinery
35:57
from latching on, effectively silencing the gene.
36:01
The cell can chemically modify those histone
36:03
spools we talked about earlier. If the cell attaches
36:06
an acetyl group to the histones, the spools relax
36:09
their magnetic grip on the DNA, unwinding it
36:12
slightly so the reading machinery can access
36:14
it. So the DNA isn't just a static string of
36:16
code sitting there passively. It is constantly
36:18
being physically folded, tagged, hidden, and
36:21
exposed in response to the environment. The sheer
36:24
level of control is mind -bending. And knowing
36:27
how tightly regulated this is brings us perfectly
36:29
to busting one of the most irritating tropes
36:31
in popular science media. Ah, the gene for myth.
36:34
Yes. You see a headline that says, scientists
36:36
discover the gene for height or the gene for
36:39
intelligence or a gene for aggressive behavior.
36:41
It's everywhere. It is a fundamentally flawed
36:44
way of communicating genetics. It treats genes
36:47
like singular on -off switches for incredibly
36:49
complex physical and behavioral outcomes. Now,
36:52
to be clear, single gene conditions do exist.
36:56
We discussed sickle cell, where one typo in one
36:58
gene definitively causes the disease. Huntington's
37:01
disease and cystic fibrosis are other examples.
37:04
But these are rare exceptions to the overall
37:06
rule of biology. For the vast majority of what
37:09
makes you who you are, you can't point to a single
37:11
spot on the twisted ladder and say, that's the
37:13
tall gene. You cannot. Most human traits, height,
37:17
intelligence, risk for heart disease, susceptibility
37:20
to depression, are polygenic. Poly meaning many.
37:24
These traits are the culmination of hundreds,
37:26
sometimes thousands, of different genetic variants
37:28
scattered across your entire genome. Each individual
37:31
variant might only contribute a millimeter to
37:33
your height or a microscopic fraction of a percent
37:36
to your disease risk. It's a massive collective
37:38
chorus of genes, not a single soloist. And even
37:40
then, the DNA isn't the final word because it
37:42
interacts with the physical environment, right?
37:44
Environmental interaction is half the equation.
37:47
Let's stick with height. You could inherit a
37:49
polygenic profile that gives you the biological
37:51
potential to be six feet tall. But if you suffer
37:54
from severe malnutrition during childhood or
37:56
a chronic illness that diverts your cellular
37:59
energy away from bone growth, your environment
38:01
will physically restrict your growth. You will
38:04
not reach six feet, regardless of what the manual
38:06
says. The environment intercepts the instructions,
38:08
which brings us to a quote from the source material
38:11
that serves as a profound anchor for anyone trying
38:13
to understand their own biology. Oh, genes load
38:16
the dice. They rarely determine the throw. That
38:19
is brilliant. The sequence of your A's, T's,
38:23
G's, and C's establishes a set of probabilities.
38:26
It sets the boundaries of your biological potential.
38:28
It loads the dice. But how your life literally
38:33
manifests is determined by the unimaginably complex
38:36
interaction of those 20 ,000 genes being regulated
38:39
by epigenetics, constantly responding to your
38:42
diet, your stress levels, your environment, and
38:44
sheer chance. It is the perfect synthesis of
38:47
genes. genetics and environment. We are not rigid
38:49
biological robots executing a static code. We
38:52
are highly dynamic systems. Okay, as we enter
38:54
the final segment of our deep dive today, we
38:56
need to talk about where this science is right
38:59
now. Because we've gone from Watson and Crick
39:01
drawing models on paper in the 1950s to the massive
39:04
human genome project in the 2000s. And the acceleration
39:08
of this technology from abstract theory to routine,
39:12
life -altering medical application is breathtaking.
39:15
The technological leap in genomics over the last
39:18
two decades is arguably the most rapid acceleration
39:21
of capability in scientific history. Just look
39:23
at the physical process of sequencing and actually
39:25
reading the A's, T's, G's, and C's. When the
39:29
Human Genome Project began, they were using Sanger
39:31
sequencing, which was incredibly slow and required
39:34
immense physical infrastructure. It was a monumental
39:36
international effort to sequence that very first
39:39
complete human genome, took 13 years of continuous
39:42
work, and it cost nearly $3 billion. 13 years
39:45
and billions of dollars to... read the manual
39:47
once. Fast forward to today. The advent of next
39:52
generation sequencing relies on massively parallel
39:54
processing. Instead of reading the DNA strand
39:57
end to end, machines shatter the DNA into millions
40:00
of tiny fragments, read them all simultaneously
40:02
on microscopic flow cells, and use immense computing
40:05
power to stitch the sequence back together. And
40:08
what does that mean for the time and cost today?
40:11
Today, you can sequence a complete human genome
40:14
in roughly 24 hours, and it costs a few hundred
40:17
dollars. From $3 billion to $300. From 13 years
40:21
to a single afternoon. When the cost of reading
40:24
the blueprint drops that exponentially, it completely
40:27
democratizes the science. It moves out of elite
40:30
government research facilities and goes straight
40:32
into the diagnostic labs of your local hospital.
40:34
And the real -world impact detailed in our source
40:37
material is transforming medicine. In the realm
40:39
of rare genetic diseases, what used to require
40:42
a diagnostic odyssey, years of painful, invasive,
40:46
and often incorrect testing, can now be solved
40:48
by simply sequencing a child's genome and directly
40:51
locating the single typographical error causing
40:53
the condition. It provides immediate answers.
40:55
And it's completely revolutionizing oncology,
40:57
too. Cancer, at its core, is a disease of mutated
41:01
DNA. Exactly. Cancer occurs when the genes regulating
41:04
cell division mutate and get stuck in the on
41:07
position. Today, oncologists routinely extract
41:11
DNA from a patient's tumor and sequence it. They
41:14
aren't just guessing which chemotherapy might
41:16
work. They identify the exact molecular mutation
41:19
driving that specific tumor and prescribe targeted
41:22
drugs designed to chemically inhibit that exact
41:25
mutant protein. It is precision medicine at the
41:28
molecular level. And it extends to public health,
41:30
which we all experienced recently. When a new
41:33
pathogen emerges, we no longer have to wait months
41:35
to figure out what it is. Scientists sequence
41:37
the genome of a new virus within days. We can
41:40
watch the virus mutate in real time, tracking
41:42
the specific sequence changes to see how it moves
41:45
across borders. Genomic surveillance is now the
41:47
bedrock of epidemiology. And looking backward,
41:50
this technology is rewriting our understanding
41:52
of human history. Paleogenetics allows us to
41:54
extract highly degraded DNA fragments from the
41:57
bones of ancient hominins that have been buried
41:59
in caves for tens of thousands of years. We are
42:02
reading the manuals of species that don't even
42:04
exist anymore. And by comparing those ancient
42:07
sequences to modern human DNA, we have physically
42:10
mapped out the migration routes of our ancestors.
42:13
We even discovered that early humans successfully
42:15
interbred with Neanderthals because the exact
42:18
DNA sequences inherited from those ancient encounters
42:21
are still physically present in the genomes of
42:23
billions of people alive today. The manual holds
42:26
the history of our species, but the source material
42:29
notes that we are already crossing the next great
42:31
threshold. Because we have mastered reading the
42:34
code, we can find the typos, but now we have
42:37
the tools to actively rewrite it. The development
42:40
of gene editing technologies, most notably CRISPR
42:43
-Cas9, has fundamentally changed our relationship
42:46
with biology. CRISPR is essentially a bacterial
42:49
immune system that scientists have repurposed
42:51
into programmable molecular scissors. So we can
42:54
program a piece of guide RNA to find a specific
42:57
sequence, say the single T mutation that causes
43:00
sickle cell disease. The Cas9 enzyme acts as
43:02
the scissors, physically cutting the DNA at that
43:04
exact location. And then we can provide the cell
43:07
with the correct sequence to patch the hole.
43:09
The ability to intentionally edit the letters
43:11
of the manual inside a living organism is a power
43:15
of unimaginable consequence. It holds the promise
43:18
of permanently curing genetic diseases at the
43:20
source, but it also opens profound questions
43:23
about ecological engineering and the permanent
43:25
alteration of the human germline. It is a scientific
43:28
frontier so massive with technical mechanics
43:31
so intricate that it absolutely demands its own
43:35
dedicated deep dive in the future. We are just
43:37
scratching the surface of what active editing
43:39
means for the future of life on Earth. I agree
43:42
completely. Transitioning from readers of the
43:44
code to authors of the code is the defining scientific
43:47
narrative of our century. Well, looking back
43:50
at what we have uncovered today, it has been
43:52
a monumental descent into the architecture of
43:54
life. We started by looking at our own bodies,
43:57
zooming past the trillions of cells, directly
44:00
into a microscopic nucleus just a few thousandths
44:03
of a millimeter wide. We unraveled the impossible
44:05
two meter length of the twisted ladder, freeing
44:08
it from the magnetic grip of the histone spools.
44:10
We examine the physical lock -and -key physics
44:12
of hydrogen bonds that dictate the strict pairing
44:15
of the A, T, G, and C alphabet. We watch the
44:18
massive mechanical stress of helicase unzipping
44:21
the strands and polymerase pulling loose chemical
44:23
letters out of the fluid to build perfect backup
44:26
copies. We followed the temporary mRNA blueprints
44:30
out onto the factory floor, where the ribosome
44:32
chemically translates those three -letter codons,
44:35
linking amino acids together until they fold
44:37
into the dynamic protein machines that perform
44:40
every action keeping us alive. And we confronted
44:42
the paradox of replication. We saw how a physical
44:46
typo, like a UV photon, fusing thymines together
44:49
can result in the devastating reality of a misfolded
44:52
hemoglobin protein. While simultaneously acting
44:55
as the sole physical engine driving the staggering
44:58
evolutionary diversity of our planet, it is the
45:01
ultimate mechanical system. Four letters, governed
45:03
by physical thermodynamics, regulated by complex
45:06
chemical tagging, yielding the entirety of biological
45:09
existence. The elegance of it is what stays with
45:12
you. It is. And as we wrap up, we always like
45:15
to leave you, our listener, with a final lingering
45:18
thought, a concept that builds on the mechanics
45:20
we've discussed today, but pushes our perspective
45:22
out into the unknown. And our expert has a thought
45:25
experiment that is guaranteed to shift how you
45:28
look at the night sky. It loops back to our very
45:30
first observation. the profound universality
45:33
of this molecule. Every single living organism
45:36
on Earth, from the bacteria in the deep sea vents
45:38
to the trees in the rainforest, utilizes this
45:40
exact same sugar phosphate backbone and the exact
45:44
same A, T, G, and C chemical alphabet. So the
45:47
provocative question is this. What does the physics
45:49
of DNA mean for astrobiology? If we one day discover
45:52
life on another world. perhaps swimming in the
45:54
subsurface oceans of Jupiter's moon Europa, or
45:57
locked in the ice of Enceladus, when we find
46:00
that the laws of chemistry and thermodynamics
46:02
inherently favor this exact same twisted ladder?
46:05
Is a double helix, using Purines and Pyramidines,
46:08
the most thermodynamically stable way to store
46:10
data in the universe? Will alien life utilize
46:13
the exact same four -letter alphabet? Or is DNA
46:16
just a local, Earth -bound dialect? Will we recognize
46:19
the code, or will we have to learn to read an
46:21
entirely alien biology? R, A, T, G, and C, a
46:25
fundamental rule of the cosmos or just the way
46:27
the dice happen to roll on our one tiny rock.
46:30
I absolutely love that question. It scales the
46:32
microscopic mechanisms we just discussed to the
46:35
size of the universe. Thank you for meticulously
46:37
walking us through the physical mechanics of
46:39
this molecular manual. And thank you, the listener,
46:42
for taking this deep dive with us. The next time
46:45
you scrape your knee or digest a meal or simply
46:47
look at a mushroom growing on a fallen log, take
46:49
a second to truly visualize the billions of microscopic
46:52
twisted ladders unzipping, copying, and folding
46:55
proteins inside you at this very moment. It is
46:57
a spectacular mechanical heritage. that physically
47:00
connects us all. We warmly invite you back for
47:02
our next deep dive into the fascinating source
47:04
material of our world. Until then, stay curious.