For all the fevered work being done,however,science is still far away from the Brave New W

orld vision of engineering a perfect human or even a perfect tomato. Much more research is needed before gone therapy becomes commonplace and many diseases will take decades to conquer,If theycan be conquered at all.

In the short run,the most practical way to use the new technology will be in genetic screening. Doctors will be able to detect all sorts of flaws in DNA long before they ban be fixed. In some cases the knowledge may lead to treatments that delay the onset of trie disease or soften its effects. Someone with a genetic predisposition to heart disease,for example,could follow a low-fat diet. And if scientists determine that a vital protein is missing because the gone that was supposed to make it is defective,they might be able to give the patient an artificial version of the protein; But in other instances, almost nothing can be d one to stop the ravages brought on by genetic mutations.