It’s very basic chemistry – above 90 degrees hydrogen bonds come apart, below 70 degrees the come back together. That’s really it.
The standard metaphor for DNA is a zipper. So think of one. However, because it’s fashion, these zippers are made out of different styles of teeth (of which there are four, but they only fit together in complementary pairs, so the teeth on the left side of the zipper must complement those on the right or the zip won’t zip). Because of the pattern of these teeth in the final zip, there are a zillion different types.
You have an untidy pile of these different zips made in this way in your factory. The boss, because she’s the boss, wants you to tell her if you got a particular style of zip from the thousands you have in stock, and if you do, how many, and by the way, we have an order for a million of them. She wants everything by lunchtime.
OK, you have a prototype zip making machine and the design of the zip she wants. Your Big Zipper Manufacturing Machine makes copies of existing zips, but in a specific way, from the bottom up of the left zip and top down of the right zip. Because the sides of the zip are complementary, you can use the design in your prototype machine to make the snippet of zipper that matches both the bottom of the left and top of the right.
So you can go empty the pile of random zips into the BZMM, along with the starting snippets of zipper that match the style you want, and a pile of those individual teeth. Press the GO button.
The BZMM separates all the zips into individual left and right zips then it matches up those starting snippets. These only match the final style of zip you want. Once it’s done this, the BZMM then latches onto these starter zips and starts to build new complementary zips from those individual teeth, for the left, it assembles a matching right, and for the right, a matching left. The end result is that for every original of your desired style, you now have two.
The BZMM repeats this over and over, so from those two, you have four, then eight, and you’re exponentially manufacturing those zips (all the original styles of zips will still be there, but you’re not copying those). Because the boss specified bright red zips (it’s fashion, don’t argue), you fed the machine bright red teeth at the start. At any point, you can pull a bucket of zips out of the machine and count the red ones. With your calculator you can use the numbers of red zips at various times, and the speed the BZMM works, to calculate how many of the original zips you had in stock. Scribble this down for the boss, she asked.
In the meantime, the BZMM churns away, over and over, until you have a million red zips of the desired style. Because they’re red, the BZMM colour sorting feature boxes them all up.
It’s 11am, you’re done, so take a long coffee break, you earned it.
The BZMM is basically a PCR machine. The magic is done by the DNA polymerase, the core component that fits to the starter zip and adds new teeth. We all have DNA polymerase to copy our DNA, but someone had the bright idea that this would all go faster at higher temperatures, and well, the sort of organism that lives at high temperatures must have DNA polymerase that works at high temperatures (our DNA polymerase won’t). You can do all this at lower temperatures, but what you can do in under an hour would take several days.
