Chapter 12, Problem 29A

Summary Introduction

To describe:

The experiment that led to the One Gene- One Enzyme hypothesis

Introduction:

Beadle and Tatum were the first scientists to prove that there is a relationship between genes and proteins for which they coded. They provided evidence that a gene can code for an enzyme through their experiment on the mold Neurospora .

Answer to Problem 29A

One Gene- One Enzyme hypothesis was given by Beadle and Tatum who proved this by conducting an experiment on a mold called Neurospora. They first induced mutation in the spores of mold by exposing it to X- rays. Then they grew the irradiated spores in minimal medium and found that the spores needed supplements to grow in minimal medium. They linked with mutation in genes to disorder in specific enzymes that produce the missing amino acids.

Explanation of Solution

Normally Neurospora can grow in a minimal medium that does not contain any amino acids. Beadle and Tatum exposed spores of Neurospora to X- rays and grew them on a complete medium. The spores were mutated and to test that, they grew these irradiated spores on minimal medium. When the spores were unable to grow on minimal medium, the mutant was tested to see what amino acid it lacked. When the mutant spore was able to grow on minimal medium with supplement added to it, Beadle and Tatum hypothesized that the mutant was missing the enzyme needed to synthesize that supplement amino acid.

Beadle and Tatum came up with One Gene- One Enzyme hypothesis which stated that one gene codes for an enzyme. We now know that a gene codes for a polypeptide.