Genes contain the information required to express a particular trait can be explained by the following experiment.

G Beadle and  E Tatum set an experiment to prove that one gene possesses a particular trait and is responsible for the production of one enzyme or protein. They performed their experiment on Neurospora crassa which were nutritionally mutant.

It was proved that a single protein contains several polypeptide and each polypeptide is controlled by a separate gene. Thus, each gene expresses a particular trait. This theory was called the one-gene-one enzyme or one gene-one polypeptide hypothesis.

But after the discovery of cistron (the functional unit of gene), the theory was named as a one-cistron-one polypeptide hypothesis.