Question

explain with the experiment showing one gene one enzyme hypothesis by tantum and beadle?

Answer 1

The one gene, one enzyme hypothesis states that each gene encodes a single enzyme. to prove this hypothesis Beadle and Tatum experimented using genetic and biochemical studies of the bread mold Neurospora. they started by obtaining mutants that are unable to make specific amino acids due to a broken enzyme.

Beadle and Tatum identified bread mold mutants that were unable to make specific amino acids. In each one, a mutation had "broken" an enzyme needed to build a certain amino acid. Neurospora has a fast and convenient life cycle, one with both haploid and diploid phases, it can be grown with ease and has pathways that turn sugar, salts, and biotin into amino acids and vitamins. so they conducted the experiment using neurospora.

we first need to expose Neurospora spores to radiation to cause mutations. then the descendants of the irradiated spores were grown in complete medium. Once spores started growing colonies, a small part of the colony should be transferred into another tube containing a minimal medium. only a few colonies grow normally on complete medium and do not grow at all in minimal medium.in minimal medium, the mutants die because it could not make a particular essential molecule out of the minimal nutrients. Complete medium provides the missing molecule for them to survive. mutants in minimal medium are supplemented with either amino acids or vitamins.

• If the mutant grows in minimal medium with amino acids (but not vitamins), it is unable to make one or more amino acids.

• If the mutant grows in vitamin medium but not the amino acid medium, it is unable to make one or more vitamins. we can further find the broken pathway in each mutant through the second round of tests. This way it proves that individual genes are very well connected to specific enzymes.