Molecular Genetics: Polymerase Chain Reaction

In this video from our course on molecular genetics learn all about the polymerase chain reaction.

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Transcript

00:48

Making more copies of the same thing.

00:51

So you've got this denaturation step. Basically, you heat up the DNA, it separates the two strands.

00:56

The next step is called annealing. You lower the temperature.

00:59

And what happens here is you have little DNA primers, which are similar to the RNA primers we talked about before during replication.

01:06

These DNA primers sit on either end of the gene that you're interested in, and they basically get things started for DNA polymerase.

01:12

So in the third step of the reaction, when you increase for the extension, the polymerase binds

01:16

and it extends those primers, and goes across. So basically what you're doing is you're starting off with a single molecule of DNA...

01:21

and after one step, you get two molecules of DNA. So it's a way of amplifying every time by a factor of two.

01:32

Yeah, so you can imagine that most proteins don't like getting heated up.

01:36

...to 95 degrees Celsius over and over. It's a thermostable, it's called.

01:41

So it's basically from a bacteria that lives in heat vents, and so it has no problems being hot for long periods of time. It's a special polymerase.

01:54

What is the end game here in making all these copies?

01:58

The basic reason is because it's really hard to work with single molecules of DNA.

02:02

So for example, if you wanted to figure out the sequence of a piece of DNA from one of your cells, it's a lot harder to do that if you only have one copy...

02:08

versus if you could make multiple copies. So it helps with that.

02:10

It also helps if you wanted to clone. You can't really clone very well with a single piece of DNA, but if you had multiple copies, it would be much easier to do that.

02:20

Then we combine the multiple pieces back together, and that's what's called recombinant DNA?

02:30

Recombinant DNA is actually...you take a single one of those copies and put it into a new backbone.

02:36

So recombinant basically means you're taking DNA from two different sources and putting them into one place.

02:42

Give us an example. Like, walk us through one slip of DNA that would be an obvious use case.

02:47

So one really cool thing that scientists have done is for people who have diabetes...they need to get insulin.

02:53

They used to get it from pigs and cadavers, which is not ideal for many reasons.

02:57

And so you can actually take the human insulin gene that you made through, say, RTCPR...

03:01

and you insert it into a backbone, and then you put it into bacteria, and then the bacteria will make the insulin for you.