PCR for the Masses

Admittedly, molecular biology and synthetic biology have historically been hobbies for the well-off and well-to-do. At least, that is, if a researcher wanted quality equipment. A recent Do It Yourself (DIY) revolution (a.k.a. the Maker revolution, which is closely allied with the Open Source revolution) is attempting to change all that. Here we present to you one example of how clever people are working to bring the tools of biotechnology to your garage or bedroom laboratory. Meet OpenPCR.

PCR

The Polymerase Chain Reaction (PCR) is basically the copy-machine of the biotech world. As you are well-aware, DNA is microscopic. It's miniscule. It's hard to deal with if you only have one copy because it's just too darn tiny. It's too small to pick up with tweezers and manipulate. As we mentioned in an earlier post, molecular biologists manipulate DNA (cut, paste, copy, etc.) using enzymes (also mentioned in a previous post). However, enzymes and DNA aren't like magnets. When they're in a tube of water together, they don't automatically attract each other. They're more like marbles that are let loose in the space shuttle. They bounce around with no particular attraction towards one another. They have to be lucky to collide. If you only have one copy of the DNA piece you want to manipulate, then it's not very likely your enzyme will run into it, and it's not likely you'll be able to do anything with it if it did.

The solution? Make LOTS of copies of your DNA piece. Maybe one or ten pieces of DNA won't be very likely to run into your enzyme. But, how about a billion copies? And maybe a few million enzymes? That's the secret to molecular biology. Make lot's of copies. Then, they're bound to run into each other.

Molecular Xerox

Here's how it works:

1. The molecular biology first needs to order TAQ polymerase. Polymerase, if you remember, is an enzyme that makes a copy of a single strand of DNA by using the original strand as a template. TAQ polymerase is especially cool because it can work at high temperatures (many other polymerases degrade if the temperature gets too high).
2. The molecular biologist now orders primers. Primers are small pieces of DNA that flank the region the molecular biologist wants to copy. The small, complimentary pieces of DNA bind to the matching sequence on the original strand. These provide "handles" for the polymerase to grab (polymerase can't make a copy without a blunt end of DNA to start from).
3. With these ingredients mixed in a tube (with some minerals/salts to keep the enzymes happy), the tube is placed in a PCR machine that promptly raises the temperature to near boiling to pull apart the double-stranded DNA (this is why TAQ polymerase needs to handle high temperatures).
4. The temperature lowers to around 60 C so that the primers can bump into a copy of the DNA and bind (if it's too cold, non-specific binding or "accidental" binding can happen). 
5. The temperature is raised to around 70 C to allow the polymerase to work its magic and copy the strand, starting at the primer. 
6. After a couple of minutes, the temperature cycle repeats from near boiling, to 60ish to 70ish. This is repeated as many times as desired.
7. "Desired repeats" depends on how many copies the molecular biologist wants. Every cycle, the number of copies doubles because each strand is copied. Theoretically, if you started with 1 strand of DNA and ran for 1 cycle, it would become 2 strands (2^1). If you ran for 3 cycles, 8 strands (2^3). On up to billions if you run for 30 cycles (2^30). 

Visualize PCR

It's a bit confusing to read about this and picture it in your head, so this video may help.

OpenPCR

When PCR was first put to use, the "PCR Machine" was a series of temperature-controlled water baths. A student would move a tube from one temperature to another over and over and over. It was expensive to pay the student, who's price may go up because of boredom.

More recently, to buy a professional PCR machine cost thousands of dollars. That's where OpenPCR comes in. The cost of PCR machines was so high that few could afford one for their basement biotech hobby shop. OpenPCR offers the designs to build your own from scratch, or they sell their own for just a few hundred dollars. This makes the necessary tools available for the hobbyists and schools. No need for an elaborate government grant or a windfall of money from a deceased uncle. You could theoretically make copies of DNA in your bedroom thanks to the pioneering efforts of the folks at OpenPCR.

DIY Bio Centers