one gene: one enzyme hypothesis

The theory that the principal function of a gene is to determine the structure of an enzyme molecule. This was based on evidence showing that the presence or absence of an enzyme in a biochemical pathway was a genetically determined characteristic, inherited as a single gene. The theory was extended to include proteins other than enzymes. Subsequent analysis showed that where a protein consists of several polypeptide chains, it is more correct to say that one gene codes for one polypeptide chain. The genes coding for the component polypeptides of an enzyme need not be closely linked.