How to Perform PCR at Home
Yes! Now you, too, can know the joys of making lots and lots of copies of your own
DNA in a
test tube -
in the privacy of your own home! You never know when you'll need some extra DNA, so stock up now while you have a chance. It's great fun for kids, too! (Okay, I admit it's not an incredibly useful thing to have, but hey, it would make an impressive
science project.) Here's what you'll need:
¹
Contact the Sustainable Sciences Institute (www.ssilink.org) to find out how you can purchase these in small, inexpensive quantities.
²
The plastic coffee stirrers are used to measure tiny quantities of the reagents you'll be using. You could order a handy dandy micropipette from Fisher, but that's pretty darn expensive. Instead, measure quantities visually by dipping your coffee stirrer into whatever reagent you're measuring, put your finger over the tip, and pull it out. Exact measurements are unnecessary; what's important are the relative quantities of reagents.
Okay! Now that you've gathered all of your supplies, wipe down your glassware and
kitchen stove and countertop with bleach to get your workspace as
sterile as possible.
To collect your DNA sample: Put a bit of the DI water in one of your test tubes. Take the cotton swab and gently scrape the inside of your cheek (or your kid's or your dog's or your
arch nemesis's cheek) with it; then, slosh the tip of the swab in the tube with the DI water. Stopper the tube and put it in the boiling water for a couple of minutes to rip open the cells and let your DNA out into the solution. You should use a
centrifuge at this point to separate the DNA from the rest of the cellular debris, but since we're going low-tech, we're not going to worry about that. Tap your tube gently with your finger to evenly distribute the DNA in the solution and use a plastic coffee stirrer to measure out a tiny amount; dilute this in DI water by a factor of 10, and then dilute that solution by a factor of 100. Put your samples on ice until you're ready to use them.
Recipe for PCR Soup:
- 100 units DI water
- 15 units buffer
- 8 units magnesium chloride
- 5 units each of the four dNTPs
- 3 units each of Β-globin primer 1 and 2
- 1 unit polymerase
- 1 drop mineral oil (for freezing your sample)
Add this solution to several of your sterile test tubes. Add DNA to all of the tubes but one (you'll want a
negative control.) Put your tubes in the 94° water for one minute; transfer them to the 60° water for 90 seconds; transfer them to the 72° water for another 90 seconds. There! You've just gone through one cycle of PCR! Don't pat yourself on the back and call it a day just yet, though: you'll need to repeat this cycle over and over and over (30+ times) to get a good amount of DNA copies.
Well, now that you're done, what do you do with your DNA? Unless you plan on doing something immediately, you should put your samples in the freezer so they won't
decay. If you just like the satisfaction of knowing that you're got some extra DNA just in case you ever need it (and even I can't think of a good scenario for that one), then pat yourself on the back and call it a day. If you want to take a look at your DNA, you'll need to run a
gel electrophoresis. This will show you whether you succeeded in creating copies of your DNA, and it's also something you can do at home. That, however, is another node for another time.
I can't take credit for this idea. Shawn Carlson of Scientific American put forth this procedure in an "Amateur Scientist" article last year. You can see the whole thing here: http://www.sciam.com/2000/0700issue/0700amsci.html