Mission to the Unknown

A thorn from a Varga plant. A thing part animal, part vegetable. Looks like a cactus. The poison attacks the brain. Rational thought is replaced by an overwhelming desire to kill. Eventually the poison seeps through the system and the victim is gradually transformed into a Varga.

If one of your work colleagues accidentally got themselves pricked by a nasty-looking thorn, then tried to kill you before transforming into a plant, you could be forgiven for being surprised. After all, it’s not as if it happens every day.

And there are good reasons why. Oh, the psychotic violence thing isn’t too hard, all kinds of chemicals can alter a person’s state of mind. Indeed whole industries – legal and illegal – are founded on just such self-administered manipulations, and there are plenty of drugs that have irrational bouts of violence as a side-effect.

No, it’s the whole turning into a plant bit that’s the problem. Plants and animals have fundamental differences, right down to the cellular level, from the way they extract energy from the environment to the chemicals they synthesise to keep themselves alive. The scale of the re-engineering that would be required to turn one into the other is staggering. Literally every cell would have to be changed into something new.

But let’s look at how it might be done. How do you turn a cell into a different kind of cell? It’s not easy. Even if you could somehow restructure a particular cell, the change won’t stick. You have to get right into the heart of the cell, and transform its DNA.

The chain of chemicals in your DNA contains the instructions for building and running, well, you. Every cell in your body contains a complete copy of this information. Inside your cells, tiny chemical factories run along sections of your DNA, assembling basic chemicals derived from breaking down food into constituent parts of your body. And as the cells are continually growing and dividing, they need to make copies of the DNA so that each new cell also carries this fundamental blueprint.

Although DNA is a complex chemical, it stores information in an essentially digital form. This means we can get some insight into how it works by looking at much simpler digital coding technology. A computer.

Whatever device you’re reading this on, it encodes the letter you are reading as binary numbers, strings of ones and zeroes, that are stored as electronic states within the computer’s memory. To pick a nice, simple example, let’s look at how a computer stores the word “WHO”.

In one common form of computer representation, called UTF 8-bit binary coding, every letter and character is represented by a sequence of eight ones and zeroes. So, for example, “W” is represented by the sequence 01010111, “H” by 01001000, and “O” by 01001111. This means the word “WHO”, constructed by sticking these codes together, is the sequence 010101110100100001001111.

Now let’s create a physical object that contains this code. Evolution has to make do with the raw materials available, so in that spirit let’s imagine we’re trying to do this in the fruit and veg section at Tesco.

Let’s use apricots to stand for 0, and cherries to stand for 1, stringing them together into a fruity chain of encoded information.. Our code for “WHO” then becomes ACACACCCACAACAAAACAACCCC, where “A” denotes the position of an apricot and C a cherry. To the uninitiated observer, this will just look like a particularly unsuccessful party snack, but anyone who knows the code can tell that it reads “WHO”

This is all well and good, but we want to be able to duplicate our code by some automatic process. The way nature does this with DNA goes something like this.

Take a load of tomatoes and grapes. Go along the chain of fruit, placing a tomato beside every apricot and a grape beside every cherry, sticking them to each other with a dab of jam. (You’ll probably want to use quite small tomatoes.) String your tomatoes and grapes together into another chain. You now have a more complicated double chain that looks like

You haven’t actually added any new information, though: it still just decodes to “WHO”. So why bother with all this palaver?

Well, here’s why. When it comes to reproducing this information, we can start at one end, pulling the chains apart from each other. As we do so, wherever we pull an apricot away from a tomato we attach a tomato to the exposed apricot and vice versa, and similarly for cherries and grapes. Once we’ve finished going all along the chain doing this, we end up with two separate chains that look just like the one we started with:

both of which say “WHO”.

And that’s how DNA replication works.

OK, it’s a bit more complicated than that. The fruits are chemicals called nucleobases – adenine, cytosine, thymine and guanine – the string is a chain of sugars and phosphates, the jam is a set of covalent hydrogen bonds and the whole thing is twisted into a spiral structure called a double helix – but you get the idea. (I’ve also cheated a bit by using a simple binary code – in real DNA, all four nucleobases are used in the coding on each strand.) The splitting and duplication is done by a complex chemical called DNA polymerase, and various other chemical machines also play their part. You can see a real-time simulation of the process in all its complex glory in this video – it’s really quite a remarkable piece of natural engineering.

The replication of DNA that is going on right now in all the living cells in your body is vital to making sure that you stay you. It’s remarkably accurate, only making a mistake every billion copies or so – which is just as well, because mistakes mean bits of you don’t behave the way they should, and grow into tumours and the like.

Now, if we’re going to transform you into a murderous alien vegetable, we’re going to have to interrupt this process somehow, interfere with it so the system that keeps you being you goes wrong, and instead you become something else.

The most obvious way to do this would be to introduce some kind of new chemical machine, one that would process the DNA just as the polymerase in your body does, but would add different chemicals to the exposed strands. these chemicals would have to have one end that looked like the A, C, G, and T chemicals that the DNA strand is expecting to be married up with, and another end that looked like a different A, C, G, or T, so as to create a new genetic code. Once this was done, the new imposter DNA would replicate and multiply, transforming the cellular makeup of the unfortunate victim.

It would have to be very carefully contrived. Even doing a transformation like this at all is barely conceivable, but keeping the organism alive all the way through the process would require genetic programming of astonishing ingenuity. And of course the chemical sabotage machines would have to be designed specifically to work on the target species.

There’s no way something like this is just going to evolve on some distant planet, ready and waiting for the first unwitting human who crosses its path. It would have to be deliberately genetically engineered.

But who on Earth would do such a thing? All this incredible effort only results in killing a few humans who happen to be stumbling around a jungle, an effect that could be much more straightforwardly achieved with a few claymore mines.

It would have to be done by some hostile intelligence, of prodigious scientific achievement with a penchant for grandiose, overly-complex schemes and a fanatical hatred of human beings. An alien race capable of conquering the Universe, and yet regularly brought low by an eccentric old man in a travelling phone box. The answer, surely, is staring us in the face.

The Varga plants were created by the Daleks.