Why was the one gene-one enzyme hypothesis later refined?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram showing how epinephrine binding to a beta-adrenergic receptor on a cell membrane activates a G-protein, which then stimulates adenylyl cyclase to convert ATP into cyclic AMP (cAMP), leading to physiological effects such as increased heart rate, blood vessel dilation, and glycogen breakdown. — Biochemistry In biochemistry, researchers study the chemical substances and processes that occur in living organisms and cells. In particular, various processes by which cells gain energy, such as epinephrine-stimulated cAMP synthesis, have been deduced through the study of biochemistry.

The one gene–one enzyme hypothesis, proposed by George Wells Beadle and Edward L. Tatum, was a foundational concept in biochemistry and genetics. While it correctly established that genes dictate the production of specific proteins, it was later refined because it was too narrow in its original scope.1

The hypothesis required refinement for two primary reasons:

Non-enzymatic proteins: It is now understood that not all genes encode enzymes; many genes instead encode structural proteins, regulatory proteins, or other functional molecules that are not enzymes.1
Complex protein structures: Some enzymes are composed of multiple distinct polypeptide chains, each of which is encoded by a separate gene. Therefore, a single enzyme may be the product of several genes rather than just one.1

These advancements reflect our deeper understanding of molecular biology, moving from the original "one gene–one enzyme" model to a more nuanced view of how genetic information directs the synthesis of diverse cellular components.1