Gene mapping

The ability to digitally store, and search, for personal genetic data certainly is a giant

scientific leap, but it raises a series of difficult ethical questions

The Guardian


The Internet search engines of Google and its predecessors — Lycos, Infoseek, AltaVista — became our indispensable guides as the world’s memory was converted from traditional analogue forms such as books, newspapers, magazines and microfilms to purely digital web pages.

This enabled standard text-search techniques to be scaled up to unprecedented levels — the secret of Google’s success is as much one of quantity as quality.

That same transition from analogue to digital has occurred in the world of molecular biology. Watson and Crick’s famous double helix not only provided a structure for DNA, but turned the inheritance it mediated from a chemical system into an informational one.

The data is stored as a sequence of molecules usually written as A, C, G and T. It turns out that the digital code of life is written not in binary (0 and 1), as with computers, but uses a completely equivalent representation based on four elements.

It was precisely 50 years after Watson and Crick’s breakthrough of 1953 that the listing of the three billion letters of our digital program was first elucidated.

The international Human Genome Project took 15 years of intensive work at a cost of some $3 billion (though this includes related projects).

The result was not the genome of any one person, but a kind of mosaic of several anonymous individuals. For research purposes, this is fine. Powerful programmes from the new field of bioinformatics — the marriage of computers and molecular biology — allow important general structures such as the genes that code for proteins, the basic building blocks of our bodies, to be spotted there, as well as the special variants whose presence predisposes us to disease.

If the genome were to refer to just one person, those same bioinformatics tools could be deployed to explore not what we have in common, but what makes each of us unique — the equivalent of typing your own name into Google, rather than carrying out a search for a neutral general term.

For this to be possible, the cost of sequencing the human genome needs to drop enormously. With a dozen companies racing towards the goal of the sub-$1,000 genome, the day when your DNA is sequenced and burnt on to a CD-Rom for roughly the cost of a conventional health checkup is not far off.

In fact, the personal genome is a kind of total health checkup — one that includes all possible genetic diseases, known and unknown. The result of every test available — for susceptibilities to various cancers, for example — would be revealed after a little genomic googling on your home computer.

As new genetic tests are devised, the results could be read off from your digital code without the need for further medical examinations.

The ready availability of results for every genetic test, present and future, is a mixed blessing.

Currently, you only carry out a particular test when you want the results — presumably when you have thought through the implications. Once personal genomes are available, all the facts about your susceptibility to medical conditions are there waiting for you on the CD-Rom, whether you want them or not. It is already hard enough for people at risk to decide whether to take a test for illnesses, such as Huntington’s, that are currently incurable, since nothing can be done in the event of a positive result.

Some serious medical conditions such as cystic fibrosis or Tay-Sachs disease occur when both parents pass on a particular variant of a gene to their child. These are known as autosomal recessive disorders.

It is quite common for those with relatives affected by such diseases to take genetic tests to establish whether they carry these variants; those with the variant gene may decide not to have children if they marry another carrier - or perhaps only to marry someone who is not.

Consider a not-too-distant future in which personal genomes are readily available. For those with relations affected by a serious medical condition, this will conveniently provide them with any genetic test they need.

But it will also offer the rest of us information about our status for these and other, far

less serious, autosomal recessive disorders that might similarly manifest themselves in children if we married a fellow carrier.

A bioinformatics programme running on a PC could easily check our genomes for all genes associated with the autosomal recessive disorders that had been identified so far.

Regular software updates downloaded from the Internet — like those for anti-virus programmes — would keep our search software abreast of the latest medical research. The question is, how potentially serious does a variant gene’s effects have to be for us to care about its presence in our DNA? Down to what level should we be morally obliged to tell our prospective partners — or have the right to ask about?

And just when is the appropriate moment to swap all these delicate DNA details? Before getting married? Before going to bed together?

Before even exchanging words? Will there one day be a new class of devices that hold our personal genomic profile in order to carry out discreet mutual compatibility checks on nearby potential partners?