Answer:
A transforming factor from a virulent strain of bacteria can make a non-virulent strain virulent.
Step-by-step explanation:
Griffith injected a mixture of heat-killed cells from virulent S strain of pneumococcus bacteria and live cells from avirulent R strains of the same bacteria into the mice.
The mice died due to infection and Griffith isolated live virulent cells from the dead mice.
He concluded that a transforming factor from heat-killed virulent S cells of the pneumococcus bacteria converted the live avirulent R cells into the virulent ones. The process was termed transformation.