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GN EXAM 3-1B

GN 311 (004) Jones Exam 3-1B Avery, MacLeod, and McCarthy's Transforming Principle Transcript: Today, we will be talking about Avery, MacLeod, and McCarty's transforming principle experiment. This experiment was conducted to further analyze Fred Griffith's discovery of transformation in 1928. He demonstrated that bacteria undergoes transformation by noticing a difference in heat-killed virulent bacteria when mixed with nonvirulent bacteria. This strain of nonvirulent took in the DNA from the environment to undergo transformation. Important terms to know are transformation, which is when DNA from the environment modifies the genome material of the cell. Nonvirulent, also known as avirulent, is bacteria that does not cause disease. This bacteria does not have a polysaccharide capsule, which makes it look rough. In contrast, virulent bacteria does have this capsule, which makes it smooth. This is why they are known as type S bacteria. Virulent bacteria causes disease. Here we will demonstrate Avery, MacLeod, and McCarthy's experiment. We have virulent cells, which cause disease. Thee cells are then heat-killed. The dead bacterial cells will still contain RNA, DNA, and protein after heat exposure. Each of these components are isolated and destroyed by an enzyme to determine which is the transforming principle. The three samples: The RNase, which removes RNA, the Protease, which removes protein, and DNase, which removes DNA are then added to a culture of nonvirulent cells. Both the RNase and Protease solutions were able to transform. However, in DNase, it did not undergo transformation. The solution with RNase was found to have both nonvirulent and virulent bacteria. This test tube contained DNA, proteins, nonvirulent and virulent bacteria. In comparison, the solution with Protease also contained both nonvirulent and virulent bacteria but had RNA instead of protein, which was destroyed by the Protease enzyme. Therefore, both of these have undergone transformation. The solution with DNase destroyed DNA and did not contain any virulent bacteria. This means that the solution without DNA present is unable to undergo transformation. This experiment found that DNA is what contains the genetic material and is therefore the transforming principle. DNA is the molecule of heredity and without it, transformation cannot occur.