DNA

Twentieth-century biologists realized that a molecule that serves
as the genetic material must have certain characteristics to explain
the properties of life: First, the genetic material must be able
to code for the sequence of amino acids in proteins and control
protein synthesis. Second, it must be able to replicate itself prior
to cell division. Third, the genetic material must be in the nucleus
of eukaryotic cells. Fourth, it must be able to change over time to
account for evolutionary change. Only one molecule, DNA (deoxyribonucleic
acid), fulfills all of these requirements.