The Pneumococcus experiment proves that:

Explanation

Transformation was first discovered by Griffith (1928) in Pneumococcus (Streptococcus pneumoniae), which causes pneumonia. Griffith injected a group of mice with nonencapsulated, rough (R), pneumococci; a second group with heat­killed encapsulated pneumococci cells, and a third group a mixture consisting of a few living nonencapsulated, rough pneumococci derived from a type S culture, and heat­killed encapsulated cells (S type). Griffith observed that the mice in the first two groups were not infected, and the mice in the third group died within a few days. The mice of the third group should have survived, as the organisms that could kill them had been killed, and the cells of the R type were incapable of causing disease. However, the mice died, and living virulent encapsulated cells of the type S were recovered from their dead bodies. It was observed by Griffith that killed encapsulated pneumococci had liberated some substance which favoured non­capsulated cells (R type) to produce a capsular substance. This substance, in later experiments, was proved to be DNA. These experiments showed that DNA is the genetic material.