PCR stands for Polymerase Chain Reaction. It’s used everywhere. We use it to amplify DNA for cloning, we use it for diagnostic tests, for DNA sequencing, for identifying pathogens, for identifying our long-lost relatives (and sometimes parents), and in forensics. If there’s a technique that involves DNA, PCR is probably involved somewhere, too.
Since PCR is such an important technique, and we’re going to be using PCR in our course, it’s worth checking out a few animations to get in the right state of mind.
Like so many things, you have to follow a bit of a convoluted path to get to the right place.
Start out by going here. When you get there, follow the path that you see below to find two PCR animations.
Both animations illustrate the steps in PCR. The first animation (Making many copies of DNA) is interactive. There is one confusing step though, after you click the link, you will reach this page:
I found that it’s not obvious to all students that you need to click the word “Amplification”. (I guess the dnai designers should read one of my favorite “Joel on Software” posts on Designing for people who have better things to do with their lives.)
Anyway, back to the animations. The first animation is very nice for students because, once they’ve solved the puzzle of starting it, they must click different buttons like “Denature DNA” to see what happens when DNA is denatured. The rest of the tutorial continues in the same vein through five cycles of PCR until you’ve amplified a specific region of DNA. There’s even a graph to show how the number of molecules of a DNA fragment increase with each cycle.
The second animation was created, so I’m told. by the people who did some of the work for the Harry Potter movies. It shows. This animation wins my vote for the one with the “Wow” factor.
The downside is that students find the second animation so convincing that they think that they’re looking at the real thing.
Still, I enjoy it. Just be sure to hit the Mute key before you start, since there’s no option to turn off the sound.
And make your students repeat this phrase: “it’s only a movie, it’s only a movie“