The ghosts in the human genome machine

The purpose of the Human Genome Project was to map all the individual bases that make up our DNA. There are four types of these bases, adenine, thymine, cytosine, and guanine, and they combine to form genes.

Now that the project has achieved its main goal and finished the sequencing, the next step is to identify the actual genes as distinct from the majority of the material, the so-called ‘junk DNA’. (Only a tiny proportion of the overall DNA actually consists of genes.)

Humans share 99.9% of their genes, and so the information discovered through the HGP is relevant to all of us. As we have about 20,000-25,000 genes, only a handful are unique to any one of us. But whose DNA was actually sequenced? The project used samples from anonymous donors. Neither the scientists nor the donors know whose samples actually ended up being sequenced, but it is clear that more than one person’s was used, i.e. the information we have is an amalgamation from different donors. Because the ‘map’ created by the HGP is actually linear – a sequence of letters corresponding to the order of bases, at any one point in the sequence, the information we have corresponds to just one unknown donor, but we don’t know who.

This deliberate uncertainty interests me. Scientists (whatever their discipline) spend so much time battling uncertainty, trying to quantify or eliminate it from their work. Much of this uncertainty is caused by random fluctuations or systematic biases in what they are trying to measure. Both need to be understood and accounted for, if you’re trying to make sense of your external world. And more fundamental uncertainties exist in quantum physics, which are not simply due to errors or limitations in the way that we measure things.

So it seems counter-intuitive to increase the amount of uncertainty in this major experiment. But clearly it has several purposes. Uncertainty about knowledge of the donors can protect them from the consequences of having their genome sequenced. For example, subsequent identification of genes relating to disease can’t be attributed back to a particular donor. Also, by banishing information on the particular donors, the experiment is able to interest everyone. It encourages us all to feel that that map has a direct relevance to each and every one of us. As a result, the project is allowed to gain a certain amount of authority.

But you could just as easily say that the project is relevant to no one. What does it mean to sequence a genome of a person that doesn’t actually exist?

This partial information is an excellent example of synecdoche, a type of metaphor in which part of a thing is used to stand in for its entirety. We don’t yet have DNA sequences for all humans, and we don’t yet know which parts of the sequence we do have are shared by all humans. So ‘The Human Genome Project’ is a misnomer.

Perhaps I shouldn’t be too harsh. In practice, it’s actually impossible to communicate without using synecdoche. Fiction writers know that they can’t get across the entirety of their fictional characters. They write about aspects of these characters, and the reader uses these a bit like dried milk, to reconstitute them and make up their own pictures.

Or you can say ‘there is nothing outside the text’, and therefore the human genome is just a sequence of bases, and we are free to give it as much or as little significance as we wish.