Reading the gene manual
Your genes are made of DNA: a chemical code with four 'letters', known as bases, arranged in pairs. The complete human instruction manual, known as the human genome, is made of three billion DNA base pairs. Only around 3 per cent of them spell out genes. Scientists don't know what, if anything, the remaining 97 per cent of your DNA does. The aim of the Human Genome Project is to read the complete manual, i.e. to sequence the entire genome.