The Human Genome Project has dished up some real surprises to scientists. The first surprise was the vast percentage of the human DNA that is inactive. It is estimated that at least 97% of our DNA is in actual fact a waste of space, as it does not contain any active genes that actually carry the code for any of our physical makeup. Then within the genes there are Introns — parts that do not carry any code; and Exons &mdash sections that carry some sort of genetic code. The full length of our DNA is made up of some 20 000 genes that have now been identified.