His death was confirmed by Cold Spring Harbor Laboratory, where he was based for much of his career, and by his son Rufus, who did not cite a specific cause. Dr. Watson was seriously injured in a car accident in 2018.

The discovery of DNA’s double helix structure — made with his research partner, Francis Crick, and collaborators Maurice Wilkins and Rosalind Franklin — forever altered the study of biology and influenced modern life in ways that extended far beyond the academic.

In a professional life spanning seven decades, Dr. Watson had a hand in scientific achievements that encouraged the rise of a flourishing multibillion-dollar biotechnology industry with applications in the fields of medicine, agriculture, forensics and green technology, among others.

DNA testing has caused a revolution in criminal justice, yielding evidence that can expose the guilty and absolve the innocent; its uses include diagnosing disease and establishing paternity and other familial relationships. Gene manipulation creates plants that are more disease- and drought-resistant and crops that are more nutritious; it makes possible cloning and fertility treatments. Gene therapy has begun to make headway in the endless fight against disease.

Although the description of DNA and the subsequent Nobel Prize largely defined Dr. Watson’s public image, those laurels represented a fraction of his accomplishments as a skilled academic scientist and administrator.

He went on to serve on the faculty at Harvard University, and he directed the Human Genome Project at the National Institutes of Health, an endeavor that mapped the 20,000-plus genes found in human chromosomes. He also played a large part in Cold Spring Harbor Laboratory’s rise to prominence as a biomedical research center.

Dr. Watson also was known for his unsparing, even mean-spirited candor when commenting on the personalities and rivalries at the cutting edge of science. A longtime colleague at Harvard, the eminent biologist Edward O. Wilson, called him “the most unpleasant human being I had ever met” and compared him to the Roman emperor Caligula, the mad degenerate who fancied himself a god.

Dr. Watson’s best-selling 1968 memoir, “The Double Helix,” not only demystified his early research for the layperson but also presented a riveting account of his life as a young man who was passionate and brilliant, insuppressibly frank and forthright. The book also foreshadowed Dr. Watson’s most troubling legacy — a history of remarks in which he veered from what he deemed unfiltered for-the-sake-of-argument provocation toward statements generally condemned as abhorrent.

For decades, he had made patronizing and sexist comments about female scientists, including Franklin, an important early colleague. He proposed a link between tropical climates and libido (the difference between “Latin Lovers” and “English patients,” he joked) and embraced “The Bell Curve,” a 1994 book by psychologist Richard J. Herrnstein and political scientist Charles Murray that proclaimed a hotly contested connection between IQ and ethnicity.

Dr. Watson relentlessly championed the discredited theory of genetic determinism and the notion that Blacks were intellectually inferior.

“All our social policies are based on the fact that their intelligence is the same as ours, whereas all the testing says not really,” he told the Sunday Times of London in 2007, referring to Black people. He added that while he once held out hope that everyone was equal, “people who have to deal with Black employees find this not true.”

That same year, he told Esquire magazine that “some antisemitism is justified” and that he shunned “the left wing because they don’t like genetics, because genetics implies that sometimes in life we fail because we have bad genes. They want all failure in life to be due to the evil system.”

And his 2007 memoir, “Avoid Boring People,” amplified what he had been saying for years about women: “Anyone sincerely interested in understanding the imbalance in the representation of men and women in science must reasonably be prepared at least to consider the extent to which nature may figure, even with clear evidence that nurture is strongly implicated.”

Dr. Watson’s comments on race, in particular, soon cost him the directorship at Cold Spring Harbor Laboratory on Long Island, which he had helped become one of the world’s foremost research institutions for genetics.

As he entered his 80s, he found himself ostracized by the scientific community. His speaking engagements dried up, and he had to sell his Nobel medal, he said, because he needed the money. The winning bidder, a Russian businessman, purchased the gold medal for $4.1  million and then promptly returned it to Dr. Watson. In an interview with the Financial Times in 2014, Dr. Watson declared himself an “unperson” and said that “no one really wants to admit I exist.”

He vanished from public view for a while. But in a PBS documentary that aired in 2019, he declined to rescind his most inflammatory statements on race and IQ. Cold Spring Harbor severed remaining ties with him.

On the PBS program, “American Masters: Decoding Watson,” he insisted that his views on race were not based on racial animus but instead were similar to his views on schizophrenia, with which his son Rufus was diagnosed in his teens.

“If the difference exists,” he said, “we have to ask ourselves, how can we try and make it better?”

Dr. Watson’s colleagues were perplexed at how much he seemed to have changed or perhaps how little they really knew the man.

“I really don’t know what happened to Jim,” MIT biologist Nancy Hopkins told the health news site Stat in 2019. “At a time when almost no men supported women, he insisted I get a PhD and made it possible for me to do so.”

She added that “Jim now holds the view that women can’t be great at anything” and that he seemed to have “adopted these outrageous positions as a new badge of honor, [embracing] political incorrectness.”

Dr. Watson and Crick conducted their DNA work at Cavendish Laboratory at the University of Cambridge. Dr. Watson arrived at Cavendish in 1951 at the age of 23, already having obtained his PhD.

He was fleeing a dull postdoctoral fellowship at the University of Copenhagen, where he had gone to study biochemistry. He later said he was propelled by a belief in his own genius and the daunting legacy of his not-too-distant cousin Orson Welles, who was all of 25 when he made “Citizen Kane” (1941), considered one of the greatest movies of all time. Dr. Watson felt a distinct family pressure: “You have till 25.”

At Cavendish, he was assigned to an office with Crick, a 33-year-old British researcher who was investigating the structure of proteins and still struggling to obtain his doctorate. Dr. Watson found that his office mate, though studying proteins, was interested in deciphering DNA’s structure.

Deoxyribonucleic acid, or DNA, is a molecule that contains hereditary information. It exists in the nucleus of every cell in an organism and is passed on from parents to offspring during reproduction.

In the race to understand DNA, Dr. Watson and Crick considered themselves underdogs competing against some of the greatest minds of their time. Despite their age difference, the two formed a strong bond through their research, which involved many long nights in the lab and brainstorming sessions at the local pub.

“Jim and I hit it off immediately,” Crick wrote of the partnership in “What Mad Pursuit,” his 1988 memoir, “partly because our interests were astonishingly similar and partly, I suspect, because a certain youthful arrogance, a ruthlessness and an impatience with sloppy thinking came naturally to both of us.”

Fueling their desire to crack the puzzle was the Cavendish rivalry with Linus Pauling, a scientist at the California Institute of Technology and the winner of two Nobel Prizes (chemistry and peace). Pauling seemed always to be on the cusp of deciphering DNA, though he incorrectly proposed a triple helix structure.

The world of molecular biologists was a tangled web of co-workers and competitors, and Pauling was also a contemporary and rival of Sir Lawrence Bragg, head of Cavendish and Dr. Watson and Crick’s boss.

In 1948, Pauling had deciphered the alpha-helix structure of proteins, creating a three-dimensional paper model, and later won the Nobel in chemistry for his work. Pauling’s alpha-helix triumph was a goad to the disappointed Bragg, bolstering Bragg’s support of Dr. Watson and Crick’s DNA research.

Dr. Watson and Crick, inspired by Pauling’s 3D modeling of protein, decided that existing X-ray crystallography images might be used to build a physical model of DNA’s structure.

Initially, they came up with a model that turned out to be incorrect when examined by Wilkins and Franklin, two colleagues at King’s College in London, who were also studying DNA. Dr. Watson and Crick had invited them to Cambridge to look at their model, and Franklin almost immediately pointed out a flaw.

“The awkward truth became apparent that the correct DNA model must contain at least 10 times more water than was found in our model,” Dr. Watson wrote in “The Double Helix.”

Annoyed and frustrated, Bragg ordered the two men to halt their DNA research. But they persisted, and several months later, they convinced Bragg that they needed to revisit the topic, lest they face a scoop by Pauling.

Relying on X-ray crystallography images made by Franklin, they came up with a new model. This time, DNA was revealed to be a “double helix,” which the National Human Genome Research Institute has described as “two strands that wind around each other like a twisted ladder.”

In April 1953, just a few months after they came up with this model, they published a paper describing it in the journal Nature. DNA’s twisted ladder unwinds during cell division, providing a template that can be copied into new cells, they reported.

The double helix was almost immediately perceived by the scientific community as one of the greatest discoveries in biology, and perhaps in all of science.

Dr. Watson was 34 when he, Crick and Wilkins were awarded the 1962 Nobel Prize in physiology or medicine “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material.” (Franklin’s contribution was significant, but she died in 1958 of ovarian cancer, and the Nobel is not awarded posthumously. It also is not given to more than three people at once.)

“Darwin’s theory of natural selection, Gregor Mendel’s explanation of the selection of genetics, and Watson and Crick’s discovery of the DNA structure — together, these three things explain life,” said biochemist and cancer researcher Bruce Stillman, the president of Cold Spring Harbor Laboratory. “Darwin tells us how we got here, Mendel tells us the nature of inheritance, and Watson and Crick, the mechanism through which it all happens — the double helix.”

The discovery vaulted Dr. Watson into a world of fame and glory that generally eludes academicians. He was profiled in popular magazines, including Vogue, and delighted in the limelight. His memoir, “The Double Helix,” which spent 18 weeks on the New York Times bestseller list, made him a household name all over again.

Initially the book was greeted enthusiastically for its blunt and gossipy tone, unusual for a book about science, as well as for its insider’s account of how the structure of DNA was discovered. Dr. Watson took aim at nearly everyone. “I have never seen Francis Crick in a modest mood,” he declared in the first sentence of the first chapter.

But in later years, a darker view prevailed, especially regarding the unkind portrayal of Franklin — whom Dr. Watson called “Rosy” even though that was not her nickname — as a difficult, stodgy woman and the way he focused on what he considered her “unfeminine” appearance.

Dr. Watson apologized for some of his comments about Franklin but continued to make tone-deaf remarks about how grateful he was for the paucity of women in science when he was starting out in the 1950s. “I might have been thinking about them instead of DNA,” he said in 2012 at the Euroscience Open Forum in Dublin. “I think having all these women around makes it more fun for the men, but they’re probably less effective.”

James Dewey Watson was born in Chicago on April 6, 1928. His father was a debt collector. His mother was an admissions officer at the University of Chicago and a Democratic Party precinct leader.

He grew up in what he once described as a “Depression-poor family” on the city’s South Side. “I was sort of trained to get pleasure from understanding the world around me, not from material things,” he told Newsday in 1988.

As a child, he enjoyed going on frequent birdwatching walks with his father, which eventually led to an interest in understanding what life was made of.

“Darwin, of course, explained life before it started, but what was the essence of life?” Dr. Watson said in 2005 at a TED conference. It was a question he asked himself often and on which the double helix’s discovery shed some light.

The young Watson was considered a boy genius. He participated on “Quiz Kids,” a popular radio show that featured children with high IQs. And at 15, he completed high school and enrolled in the University of Chicago.

While an undergraduate, he came across a transformational book by the great Austrian physicist Edward Schrödinger called “What Is Life?” In the 1944 book, Schrödinger hypothesizes that the essence of life is information, somehow stored and recorded in every organism.

“From that moment on, I wanted to be a geneticist, understand the gene and, through that, understand life,” Dr. Watson said in his TED Talk.

He completed his undergraduate degree at the University of Chicago at 19 and then went to Indiana University to pursue his doctorate in zoology.

After the discovery of the double helix, he spent time as a research fellow at Caltech and then joined the faculty of Harvard in 1955. In 1968, while maintaining his affiliation with Harvard, he became the director of Cold Spring Harbor Laboratory.

Also in 1968, the 39-year-old Watson met Elizabeth Lewis, 20 years his junior and a student at Radcliffe, the Harvard-affiliated women’s college later absorbed by the university. They married that same year. Survivors include his wife and their two sons, Duncan and Rufus; and a grandson.

Throughout his career, Dr. Watson’s professional life continued to be filled with controversy.

His raw, passionate love of science led him to set lofty goals and to forge ahead without restraint, many times generating controversy and angering colleagues.

“He was very impatient and gripped by what he thought ought to be done,” said Mark Ptashne, a molecular biologist at Memorial Sloan-Kettering Cancer Center in New York who worked with Dr. Watson at Harvard in the 1960s. “Others might say, ‘I am going to do my own work,’ but Jim was always involved in pushing his ideas onto others.”

At Harvard, Dr. Watson battled with a cadre of biologists he considered traditionalists — those who focused on ecology rather than molecular biology.

In department meetings, he unabashedly expressed his dislike of what he considered the old-fashioned faction. “He shunned ordinary courtesy and polite conversation, evidently in the belief that they would only encourage the traditionalists to stay around,” wrote Wilson, his biology colleague, in the memoir “Naturalist.”

Wilson added: “Watson evidently felt, at one level, that he was working for the good of science, and a blunt tool was needed. Have to crack eggs to make an omelet, and so forth.”

Eventually, the molecular biologists split off, forming their own department, in large part because of Dr. Watson’s persistence. Later, as the head of the Human Genome Project in the late 1980s and early 1990s, he butted heads with Bernadine Healy, then the director of the NIH.

Healy approved of the patenting of genes; Dr. Watson was fiercely opposed to it. His opposition led him to step down from his post and return to Cold Spring Harbor in 1994.

Race-related comments he made in public began to draw intense negative attention. In a lecture at the University of California at Berkeley in 2000, he commented that heavy Black people have a greater sex drive than thin White people. He said the human species might one day be genetically improved, to be made more intelligent or attractive.

In “Genes, Girls, and Gamow,” a book he published after “The Double Helix,” he wrote about his life after the discovery of the double helix. In it, he again raised the ire of colleagues, delving into their love lives and drinking habits. Dr. Watson stayed physically active, playing tennis several times a week in his 80s. About recreation, too, he had strong opinions.

“Don’t take up golf,” he wrote in “Avoid Boring People.” Any researcher who does, he said, becomes a “thank-God-it’s Friday scientist, always fighting not to fall too embarrassingly behind those peers who have sensibly chosen the less Zen but more aerobic thrill of hitting tennis balls.”