Whatever our differences as human beings are, we all think we're more like the rest of the animal world than we realize. It is said that we share 40 percent of our genetic (遗传的) structure with the simple worm. But that fact has helped Sir John Sulston win the 2002 Nobel Prize for Medicine. Sir John is the founder of the Sanger Institute in Cambridge, which was set up in 1992 to get further understanding of the human genome (染色体组). To help them do this, they turned to the worm. The nematode (线虫类的) worm is one of the earliest creatures on planet earth. It is less than one millimeter long, completely transparent and spends its entire life digging holes through sand. But it still has lots to say about human life, and what can be done to make it better. What the worm told Sir John and his colleagues was that each of cells in the human body is programmed like a computer. They grow, develop and die according to a set of instructions that are coded in our genetic make-up. Many of the diseases that humans suffer from happen when these instructions go wrong or are not obeyed. When the cell refuses to die but carries on growing instead, this leads to cancer. Heart attacks and diseases hke AIDS cause more cell deaths than normal, increasing the damage they do to the body. Sir John was the first scientist to prove the existence of programmed cell death. Sir John Sulston got a Nobel Prize for Medicine because he has ______.