Question

Which organism was used by Beadle and Tatum to propose one gene-one enzyme hypothesis?
(a)E.coli
(b)Nostoc
(c)Drosophila
(d)Neurospora

Answer 1

One gene-one enzyme hypothesis is the concept that all biochemical processes are controlled by genes, each gene governs the production of a specific enzyme, and each enzyme controls a specific metabolic function. George Beadle and Edward Tautum postulated their theory based on their work on a bread mould. It is a type of red bread mould of the phylum Ascomycota.

Complete step by step answer:
The one gene-one enzyme hypothesis was proposed by George Beadle and Edward Tatum in 1941 based on their classic work on the bread mould Neurospora crassa. They exposed N. crassa to x-rays, causing mutations. They then observed failures in metabolic pathways caused by errors in specific enzymes.This has made them to propose the "one gene, one enzyme" hypothesis. The one gene-one enzyme hypothesis is the concept that all biochemical processes are controlled by genes, each gene governs the production of a specific enzyme, and each enzyme controls a specific metabolic function. According to this hypothesis, a phenotypic character is the end product of a chain of genetically controlled enzymatic reactions. In such a reaction chain, a precursor molecule is subjected to a series of biochemical reactions in a metabolic pathway.

So, the correct answer is 'Neurospora'.

Additional information: -The key points of one gene-one enzyme hypothesis are; All biological processes in all organisms are genetically controlled, Each biochemical process involves a series of stepwise reactions.
-Each reaction is governed by a single gene. Each gene or every reaction governs the production of a specific enzyme and each enzyme mediates a specific metabolic function.
-Each reaction is catalyzed by a specific enzyme whose production is governed by a specific gene. If a particular gene undergoes mutational changes or if it becomes defective and defunct, the production of a particular enzyme will be curtailed.

Note:
-Some gene-one enzyme hypothesis is very significant in establishing a direct functional relationship between genes and enzymes.
-One gene-one enzyme hypothesis fails to provide a satisfactory explanation for two proven facts also, namely, in some instances, a single gene code for more than one enzyme
-And the production of some enzymes is controlled by more than one gene.