Dr. James Watson, the Nobel Prize-winning co-discoverer of the structure of DNA, the stuff of genes, surprised colleagues yesterday by calling for an end to government restrictions on DNA research as unneeded "nonsense."

He said "there is no evidence" that experiments in recombining DNA can do anyone any harm, the time and dollars wasted on maintaining restrictions is "enormous," and he and other scientists who recommended the precautions in the first place were "stupidly" wrong.

The emotional plea from the slender, intense Watson - who three years ago just as emotionally called for the restrictions - sent a shockwave through a National Institutes of Health advisory committee weighing changes in the restrictions.

But it did not make any of the advisers recommend abandoning them entirely without more evidence that some of the original fears of Watson and other scientists can be forgotten.

The advisers, in fact, ended a two-day public hearing with a discussion in which most of them endorsed most of NIH's new plans to modify the restrictions but keep them in effect for most researchers.

"Watson has put some questions in our mind that I think we need to consider very carefully," but "I don't think he's right - he's his usual extreme," said Dr. Walter Rosenblith, provost of Massachusetts Institute of Technology.

"Jim is speaking, I think, for a large group of scientists" - that is, a probable majority who now agree with him - and much of what he says may be correct, commented Dr. Alexander Rich of MIT, co-chairman of a National Academy of Sciences forum on the DNA problem this year. But the "prudent" and "correct" course, he said, is to modify the rules only as new evidence shows the research to be safe. It was the "extreme" Watson who, as an extremely emotional and highly original young man, joined Britain's Francis Crick to first describe the double-helix-shaped molecule which is the chemical of the genes in every organism.

Three years ago, Watson and a small group of others first warned that new experiments splitting and then "recombining" the DNA of various organisms could create new life forms having unknown powers.

The precautions have become a "disaster," Watson said yesterday, and the public has been misled into fearing "madman scenarios."

Various scientists' original fears were, mainly that a cancer virus might be let loose, or other diseases or epidemics might be created, or that scientists might cause some subtle but disastrous changes in the genes of even lowly animals or organisms to somehow disturb the whole earht's ecology.

The first two fears were the main ones Watson said and laboratory experiences have now shown that, first of all, no one has gotten sick and, second, organisms in nature exchange DNA widely without disaster.

On a scale of things to worry about, he maintained, genetic research is "trivial." And "if you worry about changing man's genetic nature," he said, "you should worry" about regulating sex. "Maybe we should have a committee there" or require that all sex be performed at Fort Detrick," he said.

But some advisory committee members said genetic research is moving humankind toward genetic engineering, so a pause now for reflection is wise and not rash.

"God forbid" what the public would have thought if scientists themselves had not called attention to some of the dangers, said Patricia King, associate law professor at Georgetwon University.

The scientific evidence on recombinant DNA's possible safety and the possible ubiquity of DNA combinations in nature is just starting to come in "and most of us haven't seen the scientific papers yet," said Dr. Robert Sinsheimer. A prominent biologist and critic of this research, he recently became chancellor of the University of California at Santa Cruz.