He added: “It would be nice to have this kind information on every patient we treat.”

Dr. Nimer also predicted that oncologists would quickly want to start looking for these mutations in their patients or in stored samples from former patients, to see if they could help in predicting the course of the disease or selecting treatments.

Studying cancer genomes has become a major thrust of research. In the past few years the government has spent $100 million dollars for genome studies in lung and ovarian cancers and glioblastoma multiforme, a type of brain tumor. But that project, The Cancer Genome Atlas, has not decoded an entire genome. So far, it has identified mutations in brain and lung cancers, also reported in Nature in September and October. One discovery is expected to affect medical practice  a mutation that can cause some patients with the brain cancer to get worse instead of better if they are given a common chemotherapy.

The person who gave her cells for the study at Washington University became not only the first cancer patient, but also the first woman to have her entire genome decoded. Her information will be available only to scientists and not posted publicly, to protect her privacy and that of her family. The only other complete human genomes open to researchers so far have come from men, two scientists known for ego as well as intellect, who ran decoding projects and chose to bare their own DNA to the world: James D. Watson and J. Craig Venter. Their genomes are available for all to inspect.

The woman at Washington University had acute myelogenous leukemia, a fast-growing cancer that affects about 13,000 people a year in the United States and kills 8,800. Its cause is not well understood. Like most cancers, it is thought to begin in a single cell, with a mutation that is not present at birth but that occurs later for some unknown reason. Generally, one mutation is not enough to cause cancer; the disease does not develop until other mutations occur.

“Most of them are just these random events in the universe that add up to something horrible,” said Dr. Timothy J. Ley, a hematologist at Washington University and the director of the study.

The researchers chose to study this disease because it is severe and the treatment has not improved in decades.

“It’s one of the nastiest forms of leukemia,” Dr. Wilson said. “It’s very aggressive. It affects mostly adults, and there’s really no good treatment for it. A very large fraction of the patients eventually will die from their disease.”