0:00 Okay, get ready for this.0:01 If you took all the DNA in your body—just one person—and stretched it out, end to end, it would reach from the Earth to the Sun and back.0:12 Not once.0:13 Over six hundred times.0:15 No.0:15 That can't be right.0:17 Six HUNDRED times?0:18 From one person?0:19 I promise!0:20 Which is just so wild.0:22 It reminds me of what we were talking about last week with entropy—how the universe has these huge, fundamental rules.0:31 Well, biology has one too.0:33 It's the ultimate set of instructions, the code for literally everything that lives.0:40 So we’re going from the code of the universe to the code of… us.0:45 Exactly!0:46 We're talking about DNA.0:48 The code of life.0:49 Okay, "code of life" sounds amazing, but what does that actually mean?0:55 Is it like computer code?0:57 A bunch of ones and zeroes?0:59 That is an EXCELLENT question.1:01 It's a fantastic analogy, but it's maybe more like...1:05 a cookbook.1:06 A cookbook with a recipe for every single part of you.1:10 A recipe for your eyes, a recipe for how your stomach digests food, a recipe for the color of your hair.1:19 A really, really big cookbook then.1:21 The biggest!1:22 And the book itself—the DNA molecule—is shaped like a twisted ladder.1:28 That famous double helix.1:30 The sides of the ladder are made of a kind of sugar and phosphate, but the rungs...1:36 the rungs are where the magic happens.1:39 The rungs are the instructions?1:42 The rungs ARE the instructions!1:44 Each rung is made of a pair of chemicals, and there are only four of them.1:50 We call them by their initials: A, T, C, and G.1:54 That's it.1:55 That's the entire alphabet for life.1:58 Wait, hold on.1:59 Four letters?2:00 You're telling me the recipe for a human being, or an oak tree, or a blue whale is written with just FOUR letters?2:09 YES!2:09 Isn't that the most elegant thing you've ever heard?2:13 The complexity isn't in the number of letters; it's in the sequence.2:19 It's how you arrange them.2:21 I mean, think about it—we make every word in the English language with just twenty-six letters.2:28 Life just does it with four.2:30 A T C G, over and over again, in a chain that's three billion letters long in humans.2:37 Okay, my mind is a little blown.2:40 So you have this...2:41 three-billion-letter-long instruction manual inside every cell.2:46 But how does a cell read it?2:48 How do you get from a string of letters to, you know, an actual eyeball?2:54 Ah, now you're asking the billion-dollar question!2:58 This is the best part.3:00 The cell can't read the whole giant book at once.3:04 So, when it needs to build something—say, a protein that helps digest sugar—it finds the right "recipe" in the DNA.3:13 That one specific section is called a gene.3:16 Right, a gene.3:17 I’ve heard that word.3:19 So the cell makes a quick, temporary copy of that gene.3:23 Think of it like photocopying one page from that giant cookbook.3:28 That copy then goes out into the cell, to the little factories called ribosomes.3:35 And the factories build the thing.3:38 The factories build the thing!3:40 They read the copy, letter by letter, and assemble a protein based on that code.3:46 And proteins, Lena, proteins do EVERYTHING.3:50 They're the bricks, the motors, the messengers, the cleanup crew.3:55 They are what you are made of.3:57 Ohhh.3:58 Okay.3:58 So the DNA is the master blueprint, locked away safe in the center of the cell.4:04 And the copies are the day-to-day work orders sent out to the construction crews—the proteins—who then go and build the thing or do the job.4:15 You've got it!4:16 That's EXACTLY it.4:18 It's a system of such incredible elegance.4:21 Wow.4:22 Yeah.4:22 That...4:22 that actually makes sense.4:25 And here's the final piece that ties it all together, the part that gives me goosebumps.4:32 That code?4:32 That A, T, C, G alphabet?4:34 It's the same for you, for me, for the spider in the corner, for the tree outside, for the bacteria in the soil.4:43 So...4:44 we're all running on the same operating system.4:47 We are all running on the same basic operating system!4:52 A gene from a jellyfish—the one that makes it glow—can be put into a mouse, and the mouse's cells will read it perfectly and make the glowing protein.5:03 Because the language is UNIVERSAL.5:06 That is...5:07 deeply strange and wonderful.5:09 It means every living thing is connected by this shared language.5:14 It's the ultimate family tree.5:17 It's the thread that connects every single living thing that has ever existed on this planet.5:24 All of the breathtaking diversity of life—every feather, every leaf, every fin—all of it written in the same four-letter alphabet.5:34 It’s the greatest story ever told, and it's written inside of you right now.
