Beadle and Tatum gave one gene one hypothesis which states that each gene in an organism controls the production of a specific enzyme. It is these enzymes that catalyse the reactions that lead to the phenotype of the organism. It was established first time in Neurospora. Rosalind Franklin discover the structure of DNA, by the use of X-ray diffraction. Hershey and Chase confirmed that DNA is the genetic material using bacteriophage. Archibald Garrod was the first to connect a human disorder, alkaptonuria with Mendel's laws of inheritance.