The key to human life, the human genetic code, was cracked by a team of scientists and engineers in the UK and US. The researchers had to read three billion chemical `letters’ which make up the human DNA molecule. They said 97% of the genome had now been mapped. The complete genome will be available within three years. Mike Dexter, director of the Wellcome Trust, which provided a third of the project’s funding, said the development could have more significance than the invention of the wheel. A rough draft of the code, hailed as one of the most important scientific achievements of all time, could revolutionise the treatment of medical conditions such as cancer and brain disorders.