The experiment of Griffith and Avery describes the transformation of genetic material in bacteria and proves that the DNA is a transformed material. For this aim the rough strain (nonvirulent) and smooth strain (virulent) of pneumococcus were used. If the virulent strain is invaded in the mouse, the animal dies. Conversely, in case of nonvirulent strain mouse stays alive. When the heat-killed virulent strain invaded into mouse did not kill it, the mixture of heat-killed virulent strain and nonvirulent strain led to the mouse's death. After isolation of this mixture from blood it was concluded that the rough strain is transformed into virulent. In other words, when the bacteria had been killed, the DNA had survived the heating process and was taken up by the rough strain. Equipped with the gene from the smooth strain (which is responsible for forming the capsule), the former rough strain bacteria were now protected from the host's immune system and could kill the mouse.