Ok, so here's info about the polymerase chain reaction. You take the sample (I used mouse tail), digest it using enzymes, then pop it in a centrifuge. After taking the liquid off the top, you pop it in the eppindorfs with another enzyme and then you pop it in a machine which cycles through temperatures.
In the olden days, you had to do it manually (which took hours) but it's a lot easier now, apparently. It heats up to 95 celcius, to get the soloution ready, then goes up to 98 for 30 seconds. This melts the DNA joins, so you get individual strands. Then 65°C for 40 seconds to bind the enzyme together. After which the temperature goes back up to 80, at which point the enzyme manages to make a new strand of DNA. This process repeats until you have enough DNA; so this is why it's used in CSIs - an itty bitty bit of DNA can be rezzed up to yield a tonne. There's rumours that it can make errors occur ("1 in 9,000 nucleotides"), but overall it's amazing! I don't really understand how the enzyme (which comes from a bacteria called "Thermus aquaticus" - that's why you have to heat it up so much; the bacteria likes hot water, so the enzyme won't denature. Incidentally, the protein only denatures at that point, so the high temperature is necessary) works, but the company who discovered its usefullness ("Hoffmann–La Roche") is rolling in it - $2 billion in royalties.
And on an entirely unrelated note, I saw the sweetest plushie; the Herpes virus! Relevant to me because I get cold sores. And only $7.99 - a steal at £4.20! Thinkgeek shall be a prime favourite when I start making my own money.