I'd like to ramble about genetics for a bit today and how big the chances are of human/animal hybrids (which some of you might be interested in).
Some people have a rather simple grasp of what is going on in the body (especially hollywood :P) and even those that are better at biology, often miss that the constant progress in genetics only results in us discovering (again and again) that it is even more complicated than we suspected. I'll try to explain the whole system in layers, just like I dived further and further into the matter during education.
This is not supposed to be a detailed explanation, I merely want to give people a sense of the scope of the whole thing. If you want to know more details just ask good old Wikipedia. It is very good on this stuff (too many bored students with internet access during lectures I guess ^^).
People familiar with this matter will much likely find it overly simplified. This is not a scientific lecture. It is to entertain and maybe grab interest to read on.
Every living being is composed of cells. Each cell has a core (nucleus) that contains the genetic code of that lifeform (DNA). Each cell contains the same code (which makes things like DNA finger printing possible). While the DNA is the blueprint, the proteins/enzymes are the workers that execute the plan.
DNA contains the carriers of the genetic information, the nucleotides. The nucleotides are mounted on a "spine", which results in the whole DNA to look like a twisted ladder (at least in the usual graphical depiction). There are 4 types of nucleotides: A, C, G, and T (often shown as colored rods in diagrams).
Three nucleotides together are a unit and “code” for one amino acid. One such a unit is called triplet.
Proteins are a long string of amino acids. There are only 21 amino acids (in humans), but 64 combinations you can make with DNA triplets (4³). That means there is redundancy in the coding (also you need a “start” and a “stop” signal). If you have a DNA strand you can tell which amino acid sequence it will produce. But if you have an amino acid sequence you can’t say exactly how the DNA strand looked.
The DNA does not directly produce proteins. It is much too large for that (and "trapped" inside the nucleus). Instead the cell makes little copies of the relevant parts it needs at the moment. Those little copies are called RNA and can leave the nucleus.
RNA is almost the same as DNA, just with some minor changes. The RNA is then read (by a protein of course ^^) and translated into an amino acid sequence, which in the end will result in a new protein. A protein is not a flat strand though, but more a ball of yarn with magnets. Some parts attract each other, while other parts push each other away. The result is that the protein folds and coils itself into its final shape automatically as it is created (kinda like a phone cord automatically forms these little twisty things on its own... do you even know what a telephone with an actual cord is?).
So far it does sound simple enough. You know what the code is to make a protein and you know what some proteins do. Nowadays you also have tools that allow you create a DNA sequence of your liking (usually you'd just order your DNA online, from a company specializing on creating any DNA sequence you specify... much easier for you). You also have tools that allow you to copy/paste that artificial DNA into the cell's DNA almost exactly as you want (might take a while and lots of tries, but it’s doable).
The whole genetic code of humans has been analyzed (of several humans actually) and is available for everyone to download.
So we have to plan and we have the tools… what is stopping us from playing god?
Well as research dug deeper it found out that the DNA sequence alone does not mean squat. Don’t get me wrong, the DNA means a lot, but it’s not enough. A fully assembled car that is missing just the fuel is 99,9999% complete but won’t move an inch no matter what you do. Sure you can honk the horn, you can activate the wiper and listen to music with the radio, but actual driving is not possible.
Nature is a bitch and has prepared a wonderfully complex puzzle for us to solve.
DNA contains crapload of waste. Stuff it doesn’t need… ever (evolution leftovers if you will). This stuff is cut out when the RNA is created. And like the snippets of a data file on a hard drive it can be all over the place (the DNA sadly has no defragmentation option).
To put analogy in your head: Imagine yourself watching a hard drive from above, writing in that incredible speed, zig-zagging over the whole surface, writing who knows what onto the hard disk. And you wanna decipher the contents from mere observation. Scientists with lots of funding have a magnifying glass to watch :3
So the nucleotide sequence your shiny million dollar sequencer spit out does not have anything to do with of the proteins you found (it might, if you are lucky… but those are proteins that were identified first)
Let’s say you identified the DNA, the RNA and you know the protein that is made. But strangely it does not look like it should. Sometimes there are some extra amino acids that are not present in the code, other times the protein looks so totally different you wonder, if you did you job right. And the explanation? Proteins that change other proteins.
So you have your DNA. Proteins come and translate it to RNA. Then more proteins come and translate it into an amino acid sequence aka new protein (protein 1). Then another protein (protein 2) is created using a totally different part of the DNA in the same way. And then protein 2, the bastard, comes and modifies protein 1. It may add a few things here, or snip off parts there, make new connections in the structure or break them, etc… tons of possibilities.
This can also happen several times, until protein 1 has the end form that fullfills a function in the cell.
Sounds complicated? But wait. It gets even better. There are even more parameters to consider. Let’s just call them “handicaps”. This list is not complete (I have much likely forgotten many and it has been years since I left school. the probably found some more in the meantime ;3)
The speed with which a protein is made can affect its function. So if you conduct experiments under ideal circumstances in the lab the protein might not be working simply because the reaction was too fast or too slow (imagine again a string of yarn with magnets. If you unwind it slowly, the first magnet will connect to the second magnet as soon as it is “available”. Unwind very fast and there might be several magnets available for the first magnet to connect to, which will alter the structure of the whole thing.
Genetic code “changes” during lifetime:
How you live can change which parts of your DNA are active. I heard the following story in school from a professor. I haven’t found a paper on the net to verify it, but I have little reason to disbelieve him.
After WWII, the people Germany had a longer period with insufficient food. So the body activated dormant parts in the DNA that made digestion more efficient. The adults from that time even inherited this information to their children, which resulted in several generations that could gain weight more easily.
Sometimes nucleotides are unfaithful to their partner and may pair up with a nucleotid they are not compatible with. You bastards!
If you build an artificial RNA you have to watch out not to make the thing compatible with itself, or it will fold together and be useless. Easiest example is a strand like this: GGGGGGGGGGGGGCCCCCCCCCCCC. G and C are pairs and this strand will form a loop with itself for sure.
Sometimes nature does this on purpose though and the loop forming is part of the proper process, so... <.<
Nature has locked the secrets of the genes behind dozens of seals. And whenever a seal is unlocked two new seals appear. Some day humans might have the ability to alter the human on purpose. But that day won't come for a very long time. So the chances are pretty much zero for a transformation within your lifetime (even if you get 100 years old).
Genetic manipulation is used at the moment mostly to alter the simplest of lifeforms (single cell lifeforms like yeast or bacteria). Manipulation of animals and plants has been done, but the changes are minimal and mostly experimental.
If you have questions don't hesitate to ask. :3
6 years, 11 months ago
10 Jan 2012 14:27 CET