The last journal about this theme was more popular than expected so I thought I'd do some more ^^ This time I want to talk about some of the methods used in genetics to change the genetic code. I don't think I can cover all in just one journal, but I will try to cover the basics and maybe also some history :3
Let's start with the probably most important discovery in Biochemistry that made it all possible. The Polymerase Chain Reaction (Short PCR). You probably heard the name. It means multiplying DNA millions and millions of times in a very short time.
Chemistry and Biology have a naming convention (using prefixes and suffixes among other things) to give the reader of a name an idea of what's behind it. For example: All sugars have -ose at the end. Glucose, Sucrose, Fructose. But more complex names are possible too, for more complicated molecules hinting to form and function (especially in organic chemistry. Learning those naming conventions is one of the biggest reason people hate org. chemistry ^^) So for example a Beerbottleopenase would be an enzyme that opens beer bottles ^^ (Scientists usually use latin or greek or other languages to make names less obvious, but I never learned any of those.)
In this case the suffix -ase tells us that an enzyme is involved. The enzyme's name is Polymerase. Poly means many of course, hinting to the multiplying function of it. And it is a very general term. Every lifeform on earth has it's own version of it (otherwise it couldn't live and procreate), although many are very similar.
The following explanation describes how a PCR is conducted.
Outside (what you would see): 1) You see some guy mixing tiny amounts of liquid together (raindrop size). 2) Then the tiny containers are put into a tiny oven. 3) 1 hour later the containers are removed from the oven. 4) PROFIT!
>.> Science is boring to watch.
Inside (what happens): First you need your sample. DNA that you wanna multiply. The DNA can be from any source, but depending on the source more or less preparation is required. Let's go for one thing you see in CSI a lot. A saliva sample taken with a swab from the inside of the mouth. The saliva contains lots of cells from the inner walls (that's why the swab is rubbed along the inside of the cheeks... to get even more cells). But the DNA in these cells is stuck inside the nucleus and behind the walls of the cell, like the insides of a walnut. So before you can process it, you need to crack the nut. That is usually done with another enzyme that breaks down the walls and releases the DNA directly into the water.
Now the actual PCR can begin (compare these steps to the steps 1-4 above): 1) You add a buffer (almost all biochemistry happens in buffers ^^) and the DNA polymerase and some other stuff you need. 2) Your sample is put into an oven. This oven can be programmed and automatically changes the temperature as needed. First it heats up to almost boiling temperature (DNA is one of the toughest biological molecule there is and very hard to destroy... that is why it is so great for forensics. It is incredibly hard to remove your DNA from a scene of crime completely). This splits the "ladder" into two strings as the backbone of the DNA is much harder than the connection of the nucleotides with each other. Afterward the oven cools down again, so the polymerase can do its work. Now that the nucleotides are lying around all naked and exposed, the pervym... i mean polymerase comes along and begins moles... rebuilding the halved DNA string. This process is called polymerization. The polymerase simply takes the proper building blocks and attaches them onto the other string until a new, complete DNA has formed. Then the oven heats up again and the process begins anew, just with double the amount of DNA. This is repeated over and over until you have enough. If you start with a single molecule and cycle 30 times (easily do-able in a hour) you could get 1073741824 copies (~1 billion copies). 3) Take the sample out of the oven. 4) PROFIT!
This is hard to describe with words alone so watch this animation. It's simple but nice. http://www.maxanim.com/genetics/PCR/PCR.htm There are tons of animations on this subject, each a little different. Just search in google if you wanna see more. Taq Polymerase: You may have noticed that name in the animation and wondered what that meant. It is simply a heat resistant version of the DNA polymerase found in us humans. If you boil human polymerase it is destroyed (don't forget DNA is the Superman of the biomolecules... most are not as tough). And at the beginning when PCR was discovered, exactly that happened. So after each heating step you had to open the oven and put fresh polymerase into it, making the process tedious, lengthy and expensive (not to mention prone to error). Taq polymerase comes from a bacterium (Thermus aquaticus) living near volcanoes at the bottom of the ocean. The little bugger is used to living in boiling water and thus has developed a polymerase that withstands such high temperatures. So if we say DNA is Superman, than Taq polymerase is The Human Torch.
By the way, like Superman DNA has a Kryptonite. There is a special enzyme that destroys it (or rather cuts it into pieces) called DNase (deoxyribonuclease). ^^
Next time I will write about the actual tools that transfer DNA from one place to another.
PS: I found it helps me to remember stuff if I pervert it, imagining it as if it were dirty stuff. Try it if you have boring stuff to learn :P
I should totally do a science series with explicit porn content. Porn science :D With Physics Bunny and Chemistry Bunny (male and female). I can see them molesting some DNA now ^^