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frederick Griffith
He reported what is now known as Griffith's Experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly changes its form and function.He showed that Streptococcus pneumoniae, implicated in many cases of lobar pneumonia, could transform from one strain into a different strain. The observation was attributed to an unidentified transforming principle or transforming factor.This was later identified as DNA -
Oswald Avery
Oswald determined that genetic information is contained in the DNA of cells, correcting the time's widely held belief that proteins carried a cell's genetic information. His work led to extensive research on DNA. -
Erwin Chargaff
He discovered two main rules in his lifetime which were named Chargaff's rules.The first and best known achievement was to show that in natural DNA the number of guanine units equals the number of cytosine units and the number of adenine units equals the number of thymine units. the second was that the composition of DNA varies from one species to another, in particular in the relative amounts of A, G, T, and C bases. -
Rosalind Franklin
Franklin made marked advances in x-ray diffraction techniques with DNA. She adjusted her equipment to produce an extremely fine beam of x-rays. She extracted finer DNA fibers than ever before and arranged them in parallel bundles. And she studied the fibers' reactions to humid conditions. All of these allowed her to discover crucial keys to DNA's structure. Wilkins shared her data, without her knowledge, with James Watson and Francis Crick. -
Alfred Hershey and Martha Chase
Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not. Although the results were not conclusive, and Hershey and Chase were cautious in their interpretation, previous, contemporaneous and subsequent discoveries all served to prove that DNA is the hereditary material. Knowledge of DNA gained from these discoveries has applications in forensics, crime investigation. -
Watson and Crick
They determined that the structure of DNA was a double-helix polymer, or a spiral of two DNA strands, each containing a long chain of monomer nucleotides, wound around each other. According to their findings, DNA replicated itself by separating into individual strands, each of which became the template for a new double helix.
