IN the 1980s, when the Human Genome Project was starting, some critics dismissed it as a giant waste of money. Only a tiny fraction of our DNA 鈥� the figure is now put at 1.2 per cent 鈥� codes for proteins. Sequencing the non-coding stretches between these genes was futile, it was argued, because it is worthless junk.
Few would make that argument today. Although most non-coding DNA does indeed appear to be junk, some of it looks as if it may be essential. Comparisons of our genome with that of the mouse reveal that not only is much of the coding DNA very similar, so too is about 3.8 per cent of the non-coding stuff. This DNA must have a vital function 鈥� why else would it have been faithfully 鈥渃onserved鈥� ever since the ancestors of mice and men parted ways?
The real test of whether or not conserved DNA is vital is to delete bits of it to see what happens 鈥� and the first attempts to do this have produced stunning results (see 鈥淲hy our 鈥榡unk DNA鈥� may be useful after all鈥�). So far researchers have only deleted or mutated a tiny fraction of the conserved DNA to see what happens. Now we need to systematically test all the other bits, in what could be thought of as the 鈥淢inimal Mouse Genome Project鈥�. Once we know exactly what DNA is needed to produce a normal, healthy mouse, we鈥檒l have a better understanding of what it takes to make a normal, healthy human.
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