Lynn Wiley, a University of California, Davis, expert on reproductive biology who lived all aspects of her academic and personal life with remarkable intensity, died June 19 in an airplane crash in Paso Robles.

Dr. Wiley, 52, was flying a single-engine Cessna 182 as it took off from Paso Robles Municipal Airport on Saturday at about 11 a.m. A licensed commercial pilot, she was carrying four skydivers up to make a parachute jump.

The plane crashed on takeoff; an investigation into the cause is under way. Dr. Wiley and two passengers died at the scene; another died Sunday at a local hospital and the fourth was seriously injured. One of the passengers who died Saturday was Daniel Dougherty, 47, also a Davis resident and the owner of the plane Dr. Wiley was piloting.

Dr. Wiley studied flying with a focus that was characteristic of most things she did, said her husband, Jan Conroy. "She would get deeper and deeper into her interests. She was in the process of getting her Certificated Flying Instructor rating; she wanted to teach flying and would have been great at it. She also was learning to be a mechanic on our own plane, studying engine manuals, doing oil changes and doing what owners are permitted to do."

Before airplanes began taking up her free time, Dr. Wiley flew along Yolo County back roads as an avid long-distance bicyclist. She completed the Davis Double Century 12 times and the Markleeville Death Ride several times. She loved keeping fit by continuing her childhood ballet lessons as an adult, and she could be found regularly at a local athletic club on the exercise machines -- where she first met Conroy, who is director of Editorial/Design in the UC Davis Public Communications office.

In Dr. Wiley's professional life, she was a UC Davis professor of medicine, with dual appointments in the departments of obstetrics and gynecology and of cell biology and human anatomy. Dr. Wiley's research focus was the very early development of animal embryos -- the changes that occur in the first few days of the embryo's life, when it divides repeatedly to form a ball of cells and then implants in the mother's uterus.

This work in basic science had implications for studies of birth defects and cancer. Dr. Wiley examined many aspects of this process. She was the first to describe an electrical current flowing in and out of embryonic cells that helped the cells orient to one another and start the process of differentiation that leads to fetal development.

Most recently, Dr. Wiley reported that the effects of radiation can be passed down through generations. She showed that after male mice were exposed to radiation, their embryonic grandsons did not develop normally. Those grandsons that survived to maturity weighed less than normal mice and their sperm were less efficient at fertilization.

"She certainly was one of the foremost investigators in her field and was internationally respected as a scholar," said James W. Overstreet, director of the UC Davis Institute of Toxicology and Environmental Health and Dr. Wiley's supervisor. "She was very dedicated to her students, both in the classroom and in the laboratory, and had the highest standards of scientific and personal integrity."

Over the years, a number of scientific advisory panels relied on Dr. Wiley's expertise in reproduction. She was a member of two NASA committees on cell and developmental biology and of the NASA Space Science and Application Advisory Committee, which determines strategy for allocating NASA research funds. She also served four years on a committee for the National Institutes of Health, reviewing grant applications and surveying research in the physiological sciences.

One humorous result of Dr. Wiley's service on the NASA committees was that when the first married astronaut couple went into orbit in 1988, Dr. Wiley was interviewed and widely quoted about the possibilities of sex in space. She used the opportunity to suggest that NASA had neglected studies of basic biology in space -- studies that would be essential if humans were ever to deal with intimacy on very long missions, or to raise animals for food in space.

With typical candor, she said, "The bottom line is that we really don't know anything about space and sex. Zip. Sex and semen are just not topics you talk about with these guys. They shut up like clams, so we have no data."

Dr. Wiley could be counted on to bring humor and a balanced perspective to any situation, said Janet Baulch, one of Dr. Wiley's students. Baulch worked with Dr. Wiley on the studies of heritable radiation, and Dr. Wiley was there on Thursday to see Baulch get her Ph.D. in developmental biology.

At the ceremony, "Lynn was a bigger kid than I was, wanting to take her cap off because it wasn't comfortable, putting bunny ears up behind my head when I wasn't looking," Baulch said. "She was just joking and having a great time. "She was the best boss anybody could ever ask for, very caring and always willing to help you out and give you the latitude to do the kinds of things you need to do as a graduate student to succeed. And she always made sure that we not only did our academic duties but also that we exercised and had an outside life, that we were dedicated to something else beside the science."

Dr. Wiley really did delight in her students' accomplishments, said her husband. "I always thought of her students as her children. She took a personal interest in their success and worked hard for them to learn and achieve."

This year, Dr. Wiley was nominated for the prestigious UC Davis Prize for Undergraduate Teaching and Scholarly Achievement, said Joseph Silva, dean of the UC Davis School of Medicine. "Lynn's nomination had the full support of the entire school. We've lost one of our very strong teachers," Silva said. "She also was fully committed to her science and enjoyed a warm relationship with many faculty and graduate students inside and outside the medical school."

Dr. Wiley graduated from the University of California, Irvine, with a bachelor's degree in biological science in 1968 and a master's degree in radiological science in 1971, and was awarded a doctoral degree in anatomy at the University of California, San Francisco, in 1975. After a period of postdoctoral research at UCSF, she was an assistant professor of anatomy for three years at the University of Virginia. She joined the UC Davis faculty in 1984.

Lynn Wiley is survived by her husband, Jan Conroy, of Davis; her mother, Aziyad Maxey, of Laguna Beach; and several aunts, uncles and cousins. A memorial service is tentatively planned to be held in Davis during the week of June 27. For more information, contact the news service at UC Davis, (530) 752-1930. Contributions may be made to the Lynn M. Wiley Memorial Fund, with checks payable to the UC Davis Foundation, c/o University Relations, 540 Mrak Hall, University of California, Davis, One Shields Avenue, Davis, Calif. 95616.