I'm a medical technician and I need to run a DNA sequence. So I set off down the hall, happy as can be with my little sample of people skin. When I get to the lab, I suit up (put on rubber gloves), as not to contaminate the sample. I collect a bacterial colony to move into a microcentrifuge vial with a wire rod. Adding a digestive buffer to the the sample eats away at the cell wall so I can take a closer look, this takes a few hours so I twiddle my thumbs. When it's finally done "digesting" I heat inactivate the digestive enzymes using a water bath. When it's ready I move the sample to a centrifuge to be spun down into cellular debris to be removed from my sample. What I really want is the supernatant so I can move those into PCR tubes and sequence. When I've collected all the goodies i add PCR master mix. It contains water, a whole lot of nucleotides (GACT), oligonucleotide (a short nucleic acid polymer, with <50 bases) DNA primers, and a heat-stable DNA polymerase that makes the copy DNA strand longer. I'll run a positive (the one with PCR master mix) and negative (this contains deionized water) test. After my samples are prepped, I put them in the PCR machine. Yippee!!
What the PCR does is replicate DNA. It begins by splitting the double helix, next the primer of the template is annealed(a heat treatment that causes changes), and ends when the DNA polymerase is used to extend the copy of DNA. Finally, after lots of other work... I can sequence the DNA! I add sequencing brew and turn a the PCR. When that's finished I put it in a automatic sequencer and then build the sequence. I can finally compare my sample to others.