Chargaff’s Rules

26:40someone basically said there's it's a treasure map. >> Yeah, there's a treasure map and this is what it looks like and >> right and this is this a periodic crystal concept >> with a hereditary codec script which makes you can intuit it that logic. Yeah, you can you can you from first principles you can build it up and be like okay something that requires information capacity needs to be aperiodic. It needs to not be the same everywhere. Right. >> Right. Because your your level of fidelity if you just have two >> bits is very low as compared to 16 or 32 or 64. >> Yeah. And the and the order of those bits is what matters, right? You can't just be 0 1 0 1 0 1 01. It's got to be a

27:22different and that sequence is what tells you what the information is >> because DNA ultimately runs a variety of biological processes. And so like what are the how are the how are the instructions >> stored >> stored and you need a you need basically a system of enough different component parts or variables to store that complexity. >> Yeah. And so we have the treasure map and then with Watson and Crick, we have the treasure hunters. >> Yes, that's a very good way of putting it. Yeah. They they read this book and they're like, "This is a treasure that I want to find. >> Let's go find the gold of whatever. What's the What's that uh famous um

28:03place where they had all the gold, the ancient place that back in the day?" >> Yeah, I know what you're saying. I I saw I saw National Treasure, too. One of my favorite movies. It's >> the city of gold, right? >> It's the city of gold. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. Yeah. The city of gold. >> They were looking cuz frankly >> the things we live we'll get there. Sea of gold. >> It's it's so so they're trying to find this thing. They they read this book. It's an incredibly influential book for them. >> Yes. >> And they're like we want to go find what this a periodic crystal is and what does this crystal look like? >> Right. >> Okay. This is around 1944. So at this point people are are already trying to justify

28:45that DNA is really the thing that carries this genetic information. Okay. >> Winwin Churaf Chargaffin Chargaff at the University of Colombia in Manhattan I should say Colombia University um >> he uses this technique of partition chromatography to look at what is the base composition of this DNA across species. Okay. >> Okay. Because, you know, back then when um when Lavine was trying to look at the base composition, he just said everything's the same, right? There's an A, a C, a T, and a G, and they all just come together, and it's all equal parts. He didn't have the resolution >> to to to figure out if there was more A

29:27or more T and so on and so forth, right? Charge uses this new method called partition chromatography >> to quantify how much A is there in a species, >> how much T is there, how much G and how much C. As an analogy, it's like you can say, oh, it's all soda, but it's like, is it Coke? Is it Sprite? Yeah. >> Is it Fanta? >> Yeah. And are they all in equal proportions? >> Proportions, right? Like is there what is the is it Coke Zero? >> Yeah. Right. Or Diet Coke. What's the sugar volume? I'm trying to identif like create a an >> Well, there's only four different types of sodas, >> right? >> Four. So, so Coke, Sprite, Fanta, grape soda. Yeah, we'll say those four. >> And and and those are the those are the four, but Lavine has said that they're

30:08all equal and they're just creating the scaffold, right? And Char went out to say, okay, is this actually true? And he actually dismantled that hypothesis by showing that there's species specific variation. Meaning like the amount of A's and T's that I have is different from the amount that the cow has is different the from the amount that um a pig has from a bird and so on and so forth. And um he came up with a rule that said there's actually a pairing ratio. >> Okay. >> The A and the T are always the same amount. >> Interesting. and the G and the C are always the same amount. And if you look at that, um, this is this is an expert

30:51from his paper, >> the source is actually this is for humans. It it actually comes from human semen. >> Ah, we love it. >> Yeah. I mean, the these guys when you're doing science at the cutting edge, >> you got to get down into the weeds. >> You got to go to the source. >> Yeah. And and the the [laughter] advantage of human semen is like most of the stuff is DNA. I get it. It's a it's a good source >> like like with cell with normal cells there's so many proteins >> that like it's going to cloud whatever chromatography that you're doing with with human semen the sperm cell is like mostly just packaged DNA >> and a tail. >> So it's pure it's it's pure sigma pure

31:32alpha pure >> alpha. Yeah. Yeah. Exactly. Exactly. Like the most of the stuff that's in there is like your DNA. >> It's what you're looking for. >> It's what you're looking for. So, so he used that and he showed that, you know, with humans the >> the A and T's were about 35%. Yeah. >> And the C and G's were the rest. And then when he looked at, let's say, cows, he found a different ratio. >> And with pigs, he found a different ratio. But the ratios always came in these pairs. >> So the point is A and C a and C's A and T's like to hang out and C's and like to hang out. And that's true across species. across piece the the numbers could >> the portion of it is a little different but in everything the ENTs

32:15>> are are are hanging out >> and the seasons are hanging okay that's which is like another level of uh of of