James D. Watson, the grand duke of DNA, described one of his greatest fears yesterday to a packed auditorium: that society will be too scared to use genetics to make people as perfect as they can be.

Dr. Watson is one of the founding fathers of modern genetics. He was in Toronto for the respected Gairdner Foundation awards, which this year honoured the scientists who unravelled the human genome. He said the information will allow society to eradicate and prevent not only diseases but any other traits that might be deemed undesirable.

"Going for perfection was something I always thought you should do," said the 74-year-old Dr. Watson, peppering his radical perspectives with trademark humour. "You always want the perfect girl."

Would it be wonderful to turn the shy into extroverts? Calm down the hotheaded? Turn cold fish into warm human beings? As Dr. Watson sees it, the genetic revolution puts all these issues on the table.

"We'll be able to make correlations between genes and certain professions, genes for the undertaker — they really don't cry very much," he said, "or the sprinter.

"It will be an absolute flood that will start to explain everything ... even the cold fish."

Dr. Watson was younger than many of the students who came to hear him when, in 1953, he and Francis Crick discovered the molecular shape of deoxyribonucleic acid, known for short as DNA, at the famed Cavendish Laboratory at Cambridge University.

The double helix soon defined modern medicine, opened the field of molecular biology and transformed criminal justice with DNA fingerprinting that has convicted the guilty and exonerated the innocent, and that remains one of Dr. Watson's greatest prides.

But those are the field's obvious merits. The gangly, white-haired Dr. Watson, Nobel laureate, past Gairdner winner, author of seven books and recipient of 32 honorary degrees, was not at the University of Toronto's MacLeod Auditorium to rehash highlights or to reminisce.

He had come to talk about the future and the thorny issues facing society now that it has the human-genome map, which contains the precious instructions to build and operate us all: the fruit fly, the family pet, and even, Aunt Mary.

Dr. Watson took aim at scientists for not openly discussing where genetic progress may carry us.

"It's my impression that none of the genome-project leaders have gotten up and said, 'What we are going to do with this information; I think we should use it,'" he said. "Maybe they're afraid of offending people."

Never veering from controversy, Dr. Watson believes that women and their right to make reproductive choices could create the ideal future, where prenatal genetic screening keeps the sick or handicapped from ever being born and disease from being a serial killer.

In an interview earlier in the week, Dr. Watson mused that hang-gliding accidents might one day be the leading cause of death.

He is also a proponent of so-called human-germline engineering, in which doctors could add or delete elements from egg and sperm cells that will be passed down to future generations.

Perhaps adding genes that will turn slow learners into whiz kids, he said, or those to prevent smokers from ever developing lung cancer, or genes making people HIV-resistant, might be part of the future.

"But laws all over prevent DNA additives to the germlines," Dr. Watson lamented. "I'm sort of distressed when people say enhancement is bad -- the question, they wonder, is 'Who will we enhance?'"

Some of Dr. Watson's comments are unlikely to calm anyone with those thoughts, particularly when it comes to people's appearance. The Chicago-born scientist — a well-known admirer of attractive women (he titled one of his books Genes, Girls and Gamow) who keeps a 2002 calendar of tennis bombshell Anna Kournikova in his New York office — said nature can be cruel: "Who wants an ugly baby?"

Yet he admits people accuse him of wanting to use genetics "to produce pretty babies or perfect people.

"What's wrong with that?" he countered. "It's as if there's something wrong with enhancements."

Dr. Watson stressed his vision is not a bleak one. He too was haunted by the world portrayed in the 1997 film Gattaca, where genetically perfect members of an elite, conceived in labs, reign over the genetically "invalid," created naturally and condemned to society's lowest jobs.

The movie theme echoes concern that genetic enhancements will be available only to the wealthy, widening the gap between haves and have-nots. But Dr. Watson has more faith in the species: "Most humans are programmed by their genes to have compassion for their fellow man."

Dr. Watson's speech thrilled students in the audience: "It was the best lecture of the series," Seema Nagaraj, a biomedical-engineering student, said. "I appreciated his candour, that he was not afraid to state his views."