In: Biology
In some critical experiments, Avery, MacLeod and McCarty confirmed an important principle, essentially identifying DNA as the genetic material. Their experiments used rough (R) non-pathogenic bacteria, and pathogenic smooth (S) bacteria to show that a cell-free bacterial extract of the S strain was capable of converting the R strain to the S strain. What was this principle called?
This principle was called transformation.
Transformation is the mechanism by which gene transfer takes place between bacteria when the donor DNA is cell-free DNA and it is present in the immediate environment of the recipient bacterium.
Oswald Avery, Colin MacLeod, Maclyn McCarty revisited Griffith's experiment. They used rough (R) non-pathogenic bacteria and pathogenic smooth (S) bacteria. When they combined cells of R strain with DNA extract of S strain, transformation takes place.
Then they added DNase to this combination. DNase is the DNA-digesting enzyme. In this case, there was no transformation.
After that, they added RNase to the combination of cells of R strain and DNA extract of S strain. RNase is the RNA-digesting enzyme. In this case, transformation takes place.
Then they added protease to the combination of cells of R strain and DNA extract of S strain. Protease is protein-digesting enzymes. Here transformation takes place.
At last, they added RNase and protease to the same combination of cells of R strain and DNA extract of S strain. Here also transformation takes place.
So, they concluded that the transforming material was pure DNA, not protein or RNA.