In the BeadleTatum experiment UV light was used to cause DNA

In the Beadle/Tatum experiment UV light was used to cause DNA mutation in the Neurospora (bread mold) The final step was to grow the spores in individual growth factors of vitamins. What would be a possible explanation as to the state of mutations in a spore if the mutant was able to grow in complete media but not in the individual vitamins?

Solution

What would be a possible explanation as to the state of mutations in a spore if the mutant was able to grow in complete media but not in the individual vitamins?

When Beadle and Tatum bombarded the spores with X-rays, it will cause mutations in their genes. So when the organism with mutated gene is placed on a medium which lacks essential nutrients, it will die. But these mutants will grow when they kept on complete medium.

For example, if the organism’s gene coding for vitaminB6 is mutated, then it cannot grow on minimal medium, but same strain can grow when it is supplied with vitamin B6. This clearly shows that this pyridoxinless mutant is not able to synthesize vitamin B6. This gave to rise to one gene-one enzyme hypothesis. This states that each gene codes for one enzyme. If that gene gets mutated it cannot produce that particular enzyme alone.