Avery–MacLeod–McCarty identify DNA

18:29>> Yeah. >> But you actually need to be able to simplify before you can complexify for lack of a better way to put it. >> No, no, totally. And with the with the tools that they had, this is already a huge leap, right? This is showing that there is something there. There's something physically there that is transforming the bacteria to become something else. Right? The the bacteria is going from a nonviralent form to a viralent form >> and it's now has the ability to kill mice. >> Right. Even even Yes. Yes. Yes. >> Right. This is this is this is pretty crazy. And already and it it is >> and this is in 1928, >> right? So this is during like in in the

19:10middle of the two wars >> in Liverpool that that he's figured this out. >> Liverpool, >> right? >> People are trying to figure out what is that thing? >> Which makes sense. Now that we now we've pointed out like there's a mystery that is clearly identifiable and replicatable. >> Yeah. >> What is it? >> What is it? And now we get to the resolution of that with an experiment by Avery McClode and Mccardi in 1944. Okay. What they do is they systematically purify whatever the thing is that is doing this transformation. And here's what they do. They say, "Okay, there's there's possibilities, right? It could be protein. It could be RNA, or it could be DNA. What I'm going to do is I'm

19:52going to take that soup of heated up bad bacteria, >> right? and I'm going to treat it with something called trison which basically cuts a bunch of protein >> and inoculates all the proteins. It degrades all the proteins. >> So the point is if it's if protein is the source we're injecting a kill switch that kills the protein >> and so if the protein was the source uh it would not have the the bacteria would not carry >> Yeah. Yeah. And then and then mice would live. >> Mice would live, right? >> Yes. >> Um they still die. kill switch was maybe a bad terminology to use when we double kill going on. However, the point is

20:33trison killed the proteins. Proteins no longer being problematic. We put into the new mice. The new mice still die. >> The new mice still die. >> So, it's not proteins. It's not protein. >> Okay. Then we do something called RNAs, which we know is something that >> kills RNA. It cuts RNA out. >> Yeah. Okay. >> Same thing. >> Nothing. Then we do something called DNAs which is something that cuts up DNA. We know that >> that's when the mice live. Not to be confused with crisper which also cuts up DNA. >> Yes. I mean this this was a this was a very big precursor of this is this is like you know 100 years ago it's a very [laughter] specific crisper. >> Understood. >> Right. But it is it's it's a scissor and

21:14what it's doing is it's cutting up DNA. when well when you cut up the DNA that give the instructions to the bacteria to actually tell the bacteria how to infect the mice >> that's when it >> that's when that's that's when we killed that ability >> now we found the building block >> yes now we found the building block for the gene the idea of inheritance is something that is coming from DNA I actually want to take a quick step back and talk about this because at this time we did not understand how traits were passed. >> No, >> generationally >> we knew that they were from Mandel and from all these I mean obviously like I look like my parents, you look like your

21:55parents. So obviously there's something >> and then experimentally we also proved it in a controlled context to know that there there is this inheritance the concept >> of inheritance exists. >> Yes. But what it is, >> what is like what actually makes up the fabric of that? It it's actually a really important point to know like we actually didn't know that >> barely 100 years ago. >> It is it is quite incredible years ago. >> It is quite incredible. >> We didn't really know how my dad I look like my dad. >> Yeah. Yeah. This is 1944. >> That's crazy. 1944. We didn't know if it was DNA or proteins or something else. >> We We figured out how to split the atom and create nukes. Yeah, but we still

22:36didn't know why I look like my dad. >> Yeah. I mean, that just goes to show you how complicated biology is, right? And how hard it is to do experiments and really figure out what the hell is going on. >> We talk about this often where you talk about like, oh, physics. H >> Yeah, we've got that. But biology biology is tough, man. >> The variables are a little