User:Brandtc

   In the 1940’s, biochemists George Beadle and Edward Tatum made breakthrough discoveries that led to their conclusion of the One Gene – One Enzyme hypothesis.  Beadle and Tatum treated the bread mold Neurospora crassa with x-rays, which produced mutants that differed from the original mold based on their nutritional needs.  It was found that the new mutant could not survive based on the minimal medium (consisting of agar, inorganic salts, glucose, and biotin) that was supplied.  From this point, Beadle and Tatum took samples from the mutant and distributed them to different vials which held the minimal medium and an additional nutrient.  A metabolic defect was detected by the supplement that allowed growth.  The use of genetic crosses allowed the researchers to determine that not all of the mutations occurred at the same gene and where a single gene was mutated; it caused the lack of an enzyme.  The One Gene – One Enzyme hypothesis ultimately stated that the function of a gene is to dictate the production of a specific enzyme.  
   Additional research led to the revision of the One Gene – One Enzyme hypothesis.  Because proteins are gene products (and not all proteins are enzymes), biochemists began to think in the direction of one gene – one protein.  Furthermore, it was known that two or more polypeptides aid in the production of proteins, and a specific gene codes for each polypeptide.  Specific research comparing sickle cell and normal hemoglobin molecules by Pauling and Itano lead to the final modification of the hypothesis.  Beadle and Tatum’s conclusion came to be known as the One Gene – One Polypeptide hypothesis.   

[[Media:http://www.accessexcellence.org/RC/AB/BC/One_Gene_One_Enzyme.html http://www.mansfield.ohio-state.edu/~sabedon/campbl17.htm]]