DNA has a 5′→3′ directionality, with its two strands running antiparallel to each other in the double helix structure. In eukaryotic cells, DNA is tightly packaged by wrapping around histone proteins to form nucleosomes, which further organize into chromatin, allowing the genetic material to fit within the nucleus.

Key experiments by Griffith, Avery, and Hershey–Chase provided strong evidence that DNA is the molecule responsible for storing and transmitting genetic information.