Question

Beadle and Tatum used Neurospora to identify mutants affecting various biosynthetic pathways. Their research led them to develop the one gene, one enzyme hypothesis. We now know this hypothesis is too narrow in its description of genes. In what way(s) was their hypothesis is too narrow? (Check all that apply)

Check All That Apply - provide some reasoning
A. Some genes make RNAs that are not translated.
B. Many proteins in the cell are not enzymes.
C. They were unable to isolate all of the enzymes involved in methionine biosynthesis.
D. Many proteins are composed of two or more different polypeptides; so more than one gene is involved in making the functional protein.

Answer 1

The one gene, one enzyme hypothesis is too narrow because it does not account for genes producing non-translated RNAs, the myriad of proteins that are not enzymes, and the multi-subunit nature of many proteins requiring multiple genes for their assembly.

Step-by-step explanation:

Limitations of the One Gene, One Enzyme Hypothesis

The one gene, one enzyme hypothesis developed by George Beadle and Edward Tatum through their work with Neurospora crassa was groundbreaking in linking genes to specific biosynthetic pathways. However, it was too narrow for several reasons:

• Some genes produce RNAs that are not translated into proteins but have other critical functions in the cell, such as transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs).
• Many cellular proteins are not enzymes and serve various other functions within the cell, indicating that genes can code for a broad range of proteins, not just enzymes.
• The production of many functional proteins involves the assembly of multiple polypeptides, each encoded by a separate gene, making the relationship more complex than one gene coding for a single enzymatic protein. Thus, multiple genes contribute to the structure and function of these multi-subunit proteins.

As a result of these and other discoveries, the hypothesis was expanded first to 'one gene, one protein' and eventually to 'one gene, one polypeptide', reflecting the diversity of gene products beyond enzymes.