Question

Explain why the one-gene:one-enzyme hypothesis is no longer considered to be totally accurate.

Short answer

Answer: The current understanding of gene-protein relationships is more complex than the original one-gene:one-enzyme hypothesis. While the original hypothesis stated that each gene was responsible for producing a single enzyme, modern molecular biology has developed the one-gene:one-polypeptide concept, recognizing that a gene can produce a polypeptide chain that may or may not have enzymatic activity. Additionally, genetic information can be differentially spliced and regulated to produce multiple protein isoforms, increasing the proteome's complexity and the number of proteins that a single gene could potentially produce. This updated version acknowledges the complexities and exceptions of gene-protein relationships better than the original hypothesis.

Step-by-step solution

Introduce the one-gene:one-enzyme hypothesis

The one-gene:one-enzyme hypothesis was proposed by George Beadle and Edward Tatum in the 1940s. According to this hypothesis, each gene in an organism's DNA is responsible for the production of a single enzyme, and this enzyme performs a specific function in a metabolic pathway.

Describe the exceptions to the hypothesis

While the one-gene:one-enzyme hypothesis is a fundamental concept in molecular biology, there are a few exceptions to it: 1. Many genes produce RNA molecules that are not translated into proteins, such as transfer RNA (tRNA), ribosomal RNA (rRNA), and small nuclear RNA (snRNA). 2. Genes can code for more than one enzyme. Due to alternative splicing, a single gene can give rise to multiple mRNA molecules, which can result in the production of different proteins. 3. Proteins are often composed of multiple subunits, and each subunit may be encoded by a separate gene.

Explain the current understanding of gene-protein relationships

In modern molecular biology, the relationship between genes and proteins is more complex than the one-gene:one-enzyme hypothesis suggests. The one-gene:one-polypeptide concept has been developed to encompass the fact that a gene can produce a polypeptide chain, which may or may not have enzymatic activity. Moreover, genetic information can be differentially spliced and regulated to produce multiple protein isoforms, increasing the proteome's complexity and the number of proteins that a single gene could potentially produce.

Summarize the points

In conclusion, while the one-gene:one-enzyme hypothesis was a critical concept in understanding gene function and protein synthesis, it is no longer considered to be entirely accurate. With the discovery of alternative splicing, multiple mRNA molecules from a single gene, and the understanding that proteins can be formed by multiple polypeptide chains, it has evolved into the one-gene:one-polypeptide concept. This updated version acknowledges the complexities and exceptions of gene-protein relationships better.