Theodore Puck, who died at 89 of complications of a fall, was a biologist who was a key player in making it possible to work with human cells in the laboratory. His work laid the foundation for the human genome project, died November 6 in Denver.

His studies on human cells grown in the laboratory showed for the first time how little radiation was necessary to kill cells; provided insights into how chemicals in the environment affect DNA; and confirmed the precise number of chromosomes in the human genetic blueprint, which was a subject of controversy when he began his work.

Puck won the Albert Lasker Award for Basic Medical Research in 1958 as well as other prestigious awards during his 65-year career.

When Puck began his research in the 1940s, human and other mammalian cells were nearly impossible to grow in the laboratory. That meant biochemical and genetic studies had to be carried out on living humans, which precluded many types of promising studies.

Puck reasoned that the cells were not getting proper nutrients. Puck and other researchers spent months devising an appropriate cocktail of 30 to 40 individual nutrients, sugars and salts necessary for growth. They showed that precise temperature control was crucial and that the cells had to be grown in an atmosphere containing 100% humidity and 5% carbon dioxide, developing special incubators to keep the cells alive.

The techniques are now used to grow cells in laboratories throughout the world, but he never made a penny from his findings. “I was really stupid,” he said later. “I never patented anything.”

Once he was able to grow cells, it was obvious that he had a new tool for studying human genetics; previously, researchers had been limited primarily to genes in reproductive cells. He coined the term “somatic cell genetics” to cover the study of genes in cells other than sperm and eggs.

Another project concerned the effects of radiation on the cells. He found that the lethal dose of X-rays was about 1 percent of what re searchers had previously believed it to be. Those studies paved the way for the use of radiation to treat cancer by showing oncologists how much radiation they could safely use.

Puck also initiated research that finally established the number of chromosomes in the human genome at 46 pairs – not 47 or 48, as many researchers thought in the 1950s. In 1959, Puck called all the researchers working in the field to Denver, where they reached an agreement to provide a uniform numbering system. The essentials of that agreement, called the Denver System, remain in use today.

Theodore T. Puck was born in Chicago on Sept. 24, 1916. He obtained his undergraduate and graduate degrees in physical chemistry from the University of Chicago. After a series of short-term appointments, he joined the University of Colorado Medical School in 1948 and remained on the faculty until his death.

In 1962 he founded the Eleanor Roosevelt Institute for Cancer Research in Denver and led it until his formal retirement in 1995. Puck continued his work and was in his laboratory in the week before his death.