Name: 分子生物学 (Molecular Biology)
Uploaded: 2021-01-14T05:18:20.000Z
Duration: 14 min 33 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Hi. It's Mr. Andersen and in this podcast I'm going to talk about all of

molecular biology. Before I get there I want to talk about a story close to home. In the

1970s some researchers went to Yellowstone Park. They were in the geyser basin. They

pulled these bacteria out called thermus aquaticus and from that they pulled out an enzyme called

taq polymerase. That means thermos aquatic polymerase or the DNA polymerase found in

this bacteria. Cool thing about it is that it can handle really high temperatures and

survive. And the whole genetic engineering molecular biology is built upon this enzyme.

So we're talking about trillions of dollars. How much of that goes back into Yellowstone

Park? None. And so they've changed their policy on that. But it's a great way to kind of frame

this idea of molecular biology and how important it is. When I was thinking of how I wanted

to explain this in a way that makes sense I always kind of fall back on an analogy.

And so basically what I want to talk about is how we've gone over the last 30 or 40 years

to the point where we now know all the DNA inside a human. And so basically think about

it this way. Imagine if you look at these magazines right here there's a whole bunch

of information that's found inside here. There's a whole bunch of text inside here. And basically

if could I take all of the text that I want and make something out of it, like a really

cool ransom note, then I would be manipulating that text. And so I want to kind of use this

as an analogy for what we've done in molecular biology. And so what was the first thing that

was ever done? Well the first ransom note ever in the terms of molecular biology looked

something like this. And you might say that's not very impressive. Basically what is it?

It's like cutting out letters from a magazine but turning it upside down so you can't see

the letters. And so what was the first thing that we were able to do is we were able to

cut the DNA. And we do that using a restriction enzyme. But you should think of a restriction

enzyme like a scissors. It's able to cut the DNA. How do we paste DNA? Well basically to

paste DNA the glue stick equivalent of that is hydrogen bond. DNA will just come back

together again once it's been cut because of the hydrogen bonds. What's the next ransom

note? Well it would look something like this. Basically it was the first recombinant DNA.

We took DNA from a frog if I remember right. And a bacteria. And they were able to combine

those two using this hydrogen bonding. But again, a not very impressive ransom note.

Next thing that happened was something like this. So you can see in here that what we're

doing is actually ordering these little fragments cut out of a magazine from small to large.

But again you can't see what the letters are. So that's called gel electrophoresis. And

then we developed something called PCR, polymerase chain reaction, where we made a copy of that.

And so if this is that original, in PCR we make a duplicate of that. And we make an exact

duplicate. So every duplicate that we make from that is going to be exactly the same.

And that's what PCR does. It makes copies of DNA that's exactly the same. Okay. What's

the next advancement? Well the advent of the markers. So markers are basically going to

be a little section of DNA that marks that specific DNA. So if you've read that they've

found the marker or the genetic marker for breast cancer, that means that there is a

piece of DNA that's inherited by all people who have this genetically based breast cancer.

And then finally we get to where we are today. So right now we've used DNA sequencers to

figure out all of the letters inside our DNA. But it's hieroglyphics. In other words you

can't really read what it means. We know what all the letters are but we don't know where

the genes or what the genes express. In other words what proteins they make. And so when

we look at this ransom note, this is the future. This is where we want to get but we're still

quite a ways out. And so basically going back to the big things in this talk that you'll

need to remember. First one is the scissors. The role of the scissors will be played by

restriction enzymes. The roll of the glue will be hydrogen bonds that are found within

the DNA. The ruler or the measuring device is something called gel electrophoresis. To

copy that we use the polymerase chain reaction. And then to actually read it we use something

called a DNA sequencer or a gene sequencer. It's going to look at all of the letters even

though we might not know what they do, we can find them right now. So let's start with

\b0 And that's the restriction enzyme. Where do restriction enzymes come from? Well basically

they come from bacteria. Because bacteria have been locked in this million year war

with viruses. And the viruses you can see inject their DNA into the bacteria DNA. And

they make more viruses. And so how do you fight back? Well basically what they do is

they methylate their DNA. First of all what does methylate mean? You basically add a methyl

group to all of their DNA from the bacteria to protect it. And then they're going to secrete

these or create these restriction enzymes. And what the enzymes do is they chop up or

cut DNA. Since all of the bacterial DNA is protected by these methyl groups what it's

really going to chop up is all this foreign DNA. And so all of that viral DNA is broken

apart. And then the bacteria after it's done that can return to its specific shape. So

let me show you how restriction enzyme works. So if this is a section of DNA a real common

restriction enzyme is something called Eco R1. It come from the word E. coli. And this

is a restriction enzyme 1. And basically what it will do is it'll scan the DNA until it

finds this specific sequence and it's literally going to cut it in half. And so if I were

to find that, where is that going to be up here? Well you can see we have a G A A T.

So it's going to cut right like that through here. It's going to go all the way to the

end. And it's going to cut it in half like that. And so if we take a look at that basically

what will it do? It will break that into two fragments. If we take another one. Oh. Did

you see that? It came right back together again. So what brings it back together again?

There are going to be little hydrogen bonds here between those two end. And in fact we

call this a sticky end and this a stick end. Because there are going to be hydrogen bonds

that form between the two. And so once the enzyme's gone, it comes right back together

again. If we were to look at another one, this is the HindIII enzyme. Basically it's

going to cut between these two As. And so it would cut it right here. All the way down

here. And it's going to cut it into two fragments like that. If we apply that enzyme that was

found in this specific type of a bacteria, if it goes away then it comes right back together

again. What if we add both of those enzymes? What's it going to do? Well it's going to

cut it in two points or two restriction sites and then we're going to have 3 fragments that

come from that. So those are restriction enzymes. What do we use them for? In molecular biology

basically to cut DNA and then to glue it back together again. All you need is hydrogen bonds.

And so the first recombinant DNA, that of a frog and a bacteria, how did they get together?

Basically they cut them both with the same enzyme. They had the same sticky ends and

then they were able to come back together again. What's the next one that we have to

do? So what we've done is shown you how to cut. That's a restriction enzyme. How to glue.

That's hydrogen bond. Now we have to figure out how to separate the DNA according to its

length. And so to do that let me talk about Pachinko machines. Pachinko machines are essentially

these vertical machines that are really popular in Japan. You put a ball up at the top. You

usually flick the ball up at the top. And then that ball is going to bounce down. And

if it eventually goes where you want it to go, if it eventually goes into a little cup

down here at the bottom, then you might get more of those balls back. But in that case

you wouldn't. So imagine a game of Pachinko where we had one ball like this that's bouncing

its way down. And then we had instead of another ball we had like eight balls that are attached

together. So something like that. So what would happen to them if we dropped them in

a Pachinko machine? Does it make sense that they are sometimes going to go slower. They're

going to wrap around. It's going to take them way longer to get down to the bottom. And

so the single Pachinko ball would already be at the bottom where this big chain of Pachinko

balls hasn't even made it very far. And so how does that apply in DNA? Well think of