HUNTINGTON, N.Y. -- Pioneering geneticist Barbara McClintock, winner of the 1983 Nobel Prize for discovering "jumping genes," died Sept. 2 of natural causes at Huntington Hospital. She was 90.

Since 1942, Dr. McClintock performed pioneering research on Indian corn at the Cold Spring Harbor Laboratory on Long Island, N.Y. Early on, she discovered that genes can move from one area on the chromosomes to another, a finding that now helps molecular biologists identify, locate and study genes.

Dr. McClintock won a Nobel Prize in Physiology or Medicine for the phenomenon of "jumping genes" in corn, more than 32 years after publishing her discovery.

When she won the Nobel Prize, she said, "It may seem unfair . . . to reward a person for having so much pleasure, over the years, asking the maize plant to solve specific problems and then watching its responses."

James Watson, director of the Long Island laboratory and co-discoverer of the structure of DNA, called Dr. McClintock one of the three most important figures in the field of genetics.

Dr. McClintock observed gene behavior by watching the patterns of coloration in carefully cultivated maize kernels over generations.

She was the third woman to win the Nobel Prize for solo work. The other two were Marie Curie of France in 1911 for discoving radium and polonium, and Dorothy Crowfoot Hodgkin of England in 1964, for the structure of penicillin.

The scientist received many other honors, including the Lasker Award for medical research. She was named a fellow of the MacArthur Foundation, which provided her with $60,000 a year for life.

Dr. McClintock received science degrees from Cornell University in 1923 and in 1927.

A reserved woman, Dr. McClintock lived and worked on the grounds of Cold Spring Harbor Laboratory for more than 50 years. She was working as recently as four months before her death, putting in seven-day weeks and sometimes 16-hour days.

She loved her work and was embarrassed by the public acclaim she received for her accomplishments, saying she just needed her colleagues' respect.

She is survived by a sister and a brother.