hOW WAS DNA DISCOVERED?
The race for discovering DNA dates back to 1928, Biologist Fredrick Griffith performed an experiment which suggested that bacteria might be capable of transferring genetic information. He used two types of bacterial species, one type caused a type of pneumonia that is fatal to mice, and the other type was completely harmless. First Griffith injected heat treated bacteria into the mice and the mice remained healthy, the heat had killed the deadly type of bacterium. Next he injected a mixture of the harmless type and the heat treat type, thinking that it would not harm the mice, but to his surprise the mice died. Some of the harmless bacteria had transformed into and became deadly.
Later many other scientists started to search for the transforming factor. in 1944 Oswald Avery came down to two things that could be the transforming factor, proteins and DNA. to test which one was the actual transforming factor Avery added a protein-destroying enzymes to Griffiths mixture of the heat treated type and harmless type of bacterium, but the bacterial colonies were still transformed. Then he added a DNA destroying enzyme to it, this time the colonies were not able to transform. Avery;s experiment suggested that DNA is the transforming factor.
In 1952, Alfred Hershey and Martha Chase conducted experiments using viruses and bacteriophage. They observed the virus as it infected the bacteriophage, to see whether the transforming factor was protein or DNA they labeled the protein as radioactive. They observed the virus infecting the bacteriophage and noticed that no radioactivity entered the cell. After testing the protein they labeled the DNA as radioactive and observed. This time radioactivity did enter the cell, this proved to the scientific world that DNA is the "transforming factor".
Later many other scientists started to search for the transforming factor. in 1944 Oswald Avery came down to two things that could be the transforming factor, proteins and DNA. to test which one was the actual transforming factor Avery added a protein-destroying enzymes to Griffiths mixture of the heat treated type and harmless type of bacterium, but the bacterial colonies were still transformed. Then he added a DNA destroying enzyme to it, this time the colonies were not able to transform. Avery;s experiment suggested that DNA is the transforming factor.
In 1952, Alfred Hershey and Martha Chase conducted experiments using viruses and bacteriophage. They observed the virus as it infected the bacteriophage, to see whether the transforming factor was protein or DNA they labeled the protein as radioactive. They observed the virus infecting the bacteriophage and noticed that no radioactivity entered the cell. After testing the protein they labeled the DNA as radioactive and observed. This time radioactivity did enter the cell, this proved to the scientific world that DNA is the "transforming factor".