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Frederick Griffith
In January, 1928, Frederick Griffith made an important discoverey. He took two strains of bacteium ( R (rough) and S (Smooth) ) and injected them in to mice. Based on his results of the experiment, Griffith concluded that a substance could be transferred to a harmless bacteria and make them deadly. This marked an important step towards the identification of DNA as the genetic material. -
Oswald Avery
Oswald Avery led a team of scientists in the 1940's to try and answer Frederick Griffiths question: What type of substance could change the characteristcs of the organism that received it? To answer this, him and his team worked with R-strain and S-strain, mixing and inactivating DNA to find the genetic material. Based on his observations, Avery concluded that the genetic material is DNA, which was a major contribution to the field of genetics. -
Rosalind Franklin
Rosalind Franklin made a crutial contribution to the discovery of the double helix structure, but wasn't really given credit for her contributions. By using X-Rays, she was able to unearth the secret of the structure of DNA. However, it was only after her passing that Francis Crick credited her with the discovery, which, by that point, was too late. -
Erwin Chargaff
Erwin Chargaff studied DNA from many different species, and found certain rules, known as Chargaff's rules, that talked about the different nitrogen based bases of DNA, but more specifically, he was interested in four of the bases: adenine (A), guanine (G), thymine (T), and cytosine (C). Chargaff found that concentrations of the four bases differed from one species to another, but within each species, the concentrations were same. -
Alfred Hershey and Martha Chase
Alfred Hershey and Martha Chase made their discoveries in 1952. They confirmed that DNA was the genetic material by using different radioactive elements to label the DNA and proteins in viruses. This allowed them to identify which molecule the viruses inserted into bacteria. They identified the molecule to be DNA, which confirmed DNA was the genetic material. -
Watson and Crick
James Watson and Francis Crick are usually given credit for discovering that DNA has a double helix shape, like a spiral staircase. The discovery gave scientists a great understanding of the genetic structure, and really contribued to the understanding the human genome and the importance of DNA to life and health.