When the U.S. recently granted its first patent for a genetically-engineered animal, a mouse, this historic step did much more than just give new currency to that bad old joke about designer genes.

It also revived some old fears about the dangers of genetic tinkering along with some old but still misguided proposals for curtailing the risks.Essentially, those proposals come down to the notion that Congress should impose a moratorium on further such patents until the nation can debate the moral, legal, and economic implications of genetic patents and come to some kind of meeting of the minds.

But the promise and peril of genetic engineering have been apparent for a decade. Since a national debate hasn't been forthcoming in all that time, it's hard to see why one can be expected to take place now. Even if it did take place, the issues are so complex that a consensus might be a long time in coming, if indeed one could ever be produced.

Meanwhile, a moratorium might accomplish nothing but to force genetic scientists to rely on the trade secrets law, rather than the patent law, to protect their research.

Or, if that loophole were plugged, the moratorium might merely impel American scientists to pack their bags and go abroad to do their research in other countries that grant patents for living organisms.

In any case, a moratorium that supposedly protected Americans from the dangers of genetic engineering would also deprive Americans of its benefits. Among the potential benefits are more productive types of cattle and a variety of new products with considerable promise for fighting cancer and virus infections, cleaning up oil spills, and providing new sources of food.

It would be easier to feel good about the proposed moratorium on genetic patents if it didn't have to be produced by the same Congress that, in the process of producing a supposedly simpler tax law, merely sowed more complexity and confusion.

By no means, however, can it be denied that genetic engineering raises some terribly important questions. Where do we draw the line as science manipulates biological processes? Do the benefits outweigh the risks? Who decides?

Meanwhile, one point seems clear: the risks and benefits of genetic research, like those of other branches of science, depend not just on the kinds of discoveries that are made and patented but on the use to which they are put. As science pushes back the frontiers of knowledge, man's biggest challenge is not to control his technology but to control himself.