The genetic (hereditary) material in the cells of all living things is composed of DNA (deoxyribonucleic acid). The structure of DNA must enable it to store coded information that controls the biological function of cells. The genetic material transmits this hereditary information in a stable form for the cell and organism through accurate replication of DNA. Although DNA replication is not always perfect and generates mutations, the replication process ensures high accuracy in copying the genetic information so that all progeny cells, or cells resulting from the original cell, receive the same information. The DNA from all chromosomes in a human cell would be more than 6.5 feet long! Therefore, to fit inside the nucleus of a cell, DNA is packaged into chromosomes.

For more insight into the experimental facts discovered by chemists and biologists which contributed to the determination of the structure of DNA, read Discovery of DNA Structure and Function: Watson and Crick in Nature Education.