General, Non-Lecture-Specific Questions

ID #2324

Can someone please explain one gene one enzyme concept to me, versus what we understand gene expression today?

The "one gene, one enzyme" hypothesis dates back to the early 1940s when researchers George Beadle and Edward Tatum used bread mold to show that a mutation in a given gene affected one enzyme in a biosynthetic pathway. They concluded that genes specify the structure of enzymes, and one gene codes for the structure of one enzyme. This was soon found to be oversimplified since many enzymes are made up of multiple polypeptide chains (or subunits), so the hypothesis was modified to "one gene, one polypeptide" hypothesis. In reality, this too is oversimplified because some enzymes are composed of RNA as well as protein. Also, because of alternative splicing (which was discovered in the 1970s), multiple proteins can be encoded by the same gene. Another thing to keep in mind is not all proteins are enzymes, so there are plenty of genes that encode plain 'ole proteins that may not have enzymatic activity but are still important for cellular functions.

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