Odile Crick, an artist whose original sketch of the double helix of DNA, the genetic blueprint for life, became a symbol of modern molecular biology, died July 5 at her home in La Jolla, Calif. She was 86.

The cause was cancer, said her stepson, Michael Crick, who said the family had not announced Mrs. Crick’s death until July 20.

The structure of DNA, or deoxyribonucleic acid, was discovered in 1953 by Mrs. Crick’s husband, Francis H. C. Crick, and James D. Watson. The breakthrough laid the foundation for molecular biology by making it clear that the DNA molecule is the medium in which genetic information is stored and passed from generation to generation.

The double helix consists of two chains of DNA spiraling in opposite directions, each made up of four types of chemical units that are linked together. The sequence of those chemical units is the basis for genes, which signal the synthesis of the essential components of every living cell. Dr. Crick, who died in 2004, and Dr. Watson were awarded the Nobel Prize for medicine in 1962.