Political leaders of the first world are busy proclaiming that an end to genetic diseases is nigh following the completion of the Human Genome Project (HGP). Meanwhile, opponents of the project are just as vehemently proclaiming that it's the end of civilisation as we know it and marks the beginning of an era of designer babies, where people will be able to specify everything from their children's sex, to eye colour, physique and IQ. The truth lies somewhere in-between.
The blueprint, deoxyribonucleic acid, or DNA, is shared between 23 pairs of chromosomes numbered one to 22, plus either two Xs (women) or one X and one Y (men). The DNA looks like a twisted ladder with a weak hydrogen bond in the middle of each rung. On each side of the link is one of four chemicals: adenine; thymine; guanine; and cytosine which, not surprisingly, are assigned the letters A, T, G and C. Only A can pair with T while only G can pair with C. When a cell divides, the double helix separates and, as long as there's a ready supply of the appropriate chemicals within the cell, each half is able to construct a copy of its erstwhile partner because of these inflexible bonding rules.
Inside each chromosome is a bunch of genes sparsely mapped out along the double strands of the DNA. Each gene is responsible for maintaining a timely supply of a specific molecule, usually a protein, which is essential to the working of the human body. Humans can synthesise around 80,000 different proteins. Imagine each protein molecule as a folded chain (a polypeptide chain to use the vernacular) several hundred links long, where each link can be one of 20 types of amino acid. The letter sequence in the gene determines where each amino acid fits in the chain. This chain is then folded in such a way that its carbon-based 'backbone' is hidden away. This is because the backbone is 'sticky' and will readily bond with other similarly exposed molecules, seeding fibrous growth such as that implicated in Alzheimer's disease.
The numbers involved are phenomenal, hence the need for the computational power of supercomputers. Our DNA consists of about three billion base pairs (ladder rungs in the DNA) shared between our 23 chromosome pairs. Only three per cent of the DNA contains our genes, all 100,000 of them. The remaining 97 per cent of the DNA is 'junk', according to scientists.
Last June, the international HGP was completed ahead of schedule largely thanks to the collective input of 1,000 scientists in 16 labs around the world. At the same time, biotechnology company Celera also completed an initial sequencing of the human genome. The fact that the announcements appeared at the same time is probably no coincidence. The long-running, US government-backed HGP was in severe danger of being upstaged by Celera, the two-year-old private upstart which appeared to be turning in results far faster than the official initiative. On the face of it, peace was declared on 26 June 2000.
In reality, a number of key philosophical differences still separate the two parties. The HGP publishes its discoveries every 24 hours. Celera doesn't. The HGP is working, broadly speaking, for the greater good. Celera is clearly a commercial organisation. Each takes a different approach to discovering the patterns. Celera takes the whole genome, blasts it to pieces, sequences each individually then assembles the whole by looking for sequence overlaps. The public approach is hierarchical, working through the genome a known region at a time. Apart from anything else, this maps well onto the collaborative approach, which requires each laboratory to work on specific domains in order to avoid duplicating effort. Both approaches fit the discovered sequences into the physical map made public by the HGP. This gives Celera an undeniable advantage over the HGP because while it takes advantage of public information, it doesn't feel obliged to reciprocate. It does, however, plan to make its own map public later this year.
Publishing the genetic code sounds like commercial suicide. In fact, it's nothing of the sort. It's about as useful as a torn up map of the British Isles without any words or symbols. And, in its present form, many of the fragments are missing. The genomic jigsaw is likely to be completed within the next two to three years although scientists expect some small percentage to remain beyond our reach. 'It's humbling for me and awe inspiring to realise that we've caught the first glimpse of our own instruction book, previously known only to God,' sums up Dr Francis Collins, leader of the HGP.
The next step is to interpret this data and figure out what the codes mean. This is called 'annotation', and this is where the real value of the project starts to emerge.