The next step is to figure out what all the newly discovered genes actually do, says J. Craig Venter, who announced in June that his company had finished sequencing the human genome. He estimates that 60% of those human genes "are of unknown function. We're still in the very early stages of this science." "If determining the gene sequence is a hundred-yard dash, then interpreting it is a cross-country run," says another genetics expert, who worked with Venter to sequence and publish the entire fruit fly genome in 1999.
To give an idea of the amount of data scientists must sort through and analyze, Venter explains that if the fruit fly genome — all the genetic instructions for making a fly — were printed out on paper, it would take up 27,000 pages, "but the human genome is 20 times larger."Digging Deeper, from Genes to Proteins
To understand the roughly 100,000 genes in the human genome, researchers say they must investigate an even more complicated set of molecules — proteins. Genes are the basic instructions for making proteins, and the "sequence" of a gene — its structure — determines the kind of protein it makes. Some proteins become building blocks for structural parts of the cell. Other proteins become molecular "machines" that carry out the multitude of activities necessary to keep the cell and the body working properly.
With an understanding of human proteins, scientists will be able to fight diseases on many fronts. For example, scientists in Denmark have isolated a protein that may fight diabetes (糖尿病). Diabetes seems to be caused when crucial cells are accidentally killed by the body's immune system. The scientists spent years analyzing the proteins present in diabetes-prone and diabetes-resistant cells, and they tentatively concluded that the newly discovered protein protects diabetes-prone cells from being attacked by the immune system. Preliminary animal tests, in which the gene for this protein has been inserted into diabetes-prone cells, seem to confirm this hypothesis.Effective cancer drugs may also arise from a deeper understanding of genes and proteins, says Ken Croplin, president of one of the many companies working to devise new drugs based on genetic knowledge. Soon, scientists will be able to quickly and accurately compare cancer tissue with normal tissue to see which genes are "switched on" and making proteins (expressed) and which genes are not, he says.
"If you found a gene that was highly expressed in lung cancer cells but not other tissues, you could guess that that gene was involved in lung cancer," according to Croplin. "We would then try to develop in the lab a way to block the expression of that gene." One possibility would be a "small molecule" drug that would attach to the gene and shut it off, preventing that gene's protein from being produced. Finally, drugs themselves will likely become safer and more effective because they will be tailored to an individual's genetic ability to process medicines, predicts another expert. In the future, a blood test could show how much of a particular drug-processing protein a person has, which would be a measurement of that person's ability to process a certain medicine. The doctor would then adjust the dose accordingly or prescribe a drug that is custom-designed for that person's genetic structure. This new technique should eliminate many of the drug side effects that result from our current, crude methods of determining the correct dose for a given patient.
Genetic Information for All?
"It will be 10 to 20 years before we have something like a complete knowledge of all the genes and their major functions," says Croplin.However, some scientists already imagine a gigantic database（数据库）, accessible to everyone via the Internet, where scientists will publish not only the sequence of every gene but also the conclusions that have been reached about how particular genes and their proteins function in the human body.
"The future is genetic information on databases, so people can do their own research," Venter says. "The goal is to reach both physicians and individuals, and the Internet is allowing this. This will be extremely useful information for many people."For example, explains Venter, if you know your genetic code, then research on a genetics database might reveal that you have a genetic tendency for certain diseases, perhaps skin cancer. With that knowledge, you can keep an eye out for symptoms, catch the cancer early if it appears, and correct it with a simple surgery.
"My hope is that within 10 years every baby will have their complete genome sequenced and on a disk — or whatever data storage medium they're using then — before they leave the hospital," Venter says. Physicians could save time and perhaps even lives by consulting databases of genetic knowledge before they prescribe treatments, says Brent Greene, president of a genetic research company.Greene has been studying the genetic component of throat cancer. He's learned that certain treatments, promising with other forms of cancer, will not work with this form of the disease. He intends to publish his findings on the Web so that doctors won't waste time with these ineffective treatments. (Other companies post some of their findings on the Web for free, but charge a fee for access to other information.) Venter and Greene agree that people with access to such Web-based, genetic databases could, with time and research, come to know more about a particular disease and cutting-edge（最前沿的）treatments than their physician.
Finally, at least one scientist is concerned that all the talk about scientists fighting disease might give people the wrong idea about their DNA. "People have the perception that genes are full of diseases, but genes are the plans for a normal person," she says. Understanding genes ultimately means that "we will know more about normal functioning," she says, "we will enhance our knowledge about how the human body works."(Words: 1,001)
