Monday, March 2, 2009

Genetics for the geeks

DNA fingerprint
Instinctively you would have come to conclusion that the genetic information coded in living organism is digital in nature. But to hear (or rather read) this from a biologists comes to you as a, well, shock.

Imagine ... you are reading this pleasant book on biology. Dawkins is merrily going his way dumping arguments and rationale here and there, debunking the creationists, and fighting for Darwin, in general, when wham! in chapter 5 he starts discussing ROM, RAM, address, content of the address, binary. I do a double check. Have I picked up the wrong book. No! It is alright. He is trying to draw an analogy and in the process makes genetic sound so simple (not simplistic, just simple). I wish I could reproduce all the paragraphs here but that would not be fair. Instead sample this and read The Blind Watchmaker.

The information technology of the genes is digital. ... The main storage medium inside willow seeds, ants and all other living cells is not electronic but chemical. It exploits the fact that certain kinds of molecule are capable of 'polymerizing', that is joining up in long chains of indefinite length. ... Some polymers, instead of being uniform chains of one small molecule ... are chains of two or more different kinds of small molecule. ... If there are two kinds of small molecule in the chain, the two can be thought of a 1 and 0 respectively, and immediately any amount of information, of any kind, can be stored provided only that the chain is long enough. The particular polymers used by living cells are called ploynucleotides. There are two main two main families of polynucleotides in living cells, called DNA and RNA for short. ... Both DNA and RNA are heterogeneous chains, with four different kinds of nucleotides. This, of course , is where the opportunity for information storage lies. Instead of just two states 1 and 0, the information technology of living cells use four states, which may be conventionally represent as A, T, C and G.

The author then goes on to explain how the DNA is a ROM, and chromosomes are like computer tapes, and why you are different that your brother, for instance (same memory address, different content).

Were you to take this as a analogy, Dawkins, in the beginning the chapter makes it very clear:

That is not a metaphor, it is the plain truth. ... It is plain and it is true, but it hasn't long been understood.

Years ago, I had given up biology as one of my subject of choice to pursue engineering. I often look back and wondered what if ...

I can now see that two fields are not that divergent!! Of course, I am being a bit facetious.

Picture courtesy: Flávio Takemoto

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