What happened when heat-killed S cells along with R cells were injected into mice in Griffith's experiment?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) -Mice died and showed live S cells in the blood
In 1928, Frederick Griffith, in a series of experiments with Streptococcus pneumoniae (bacterium responsible for pneumonia), witnessed a miraculous transformation in the bacteria. During the course of his experiment, a living organism (bacteria) had changed in physical form.
When Streptococcus pneumoniae (pneumococcus) bacteria are grown on a culture plate, some produce smooth shiny colonies (S) while others produce rough colonies (R). This is because the S strain bacteria have a mucous (polysaccharide) coat, while R strain does not. Mice infected with the S strain (virulent) die from pneumonia infection but mice infected with the R strain do not develop pneumonia.
S strain → inject into mice → Mice died
R strain → inject into mice → Mice live
Griffith was able to kill bacteria by heating them. He observed that heat-killed S strain bacteria injected into mice did not kill them. When he injected a mixture of heat-killed S and live R bacteria, the mice died. Moreover, he recovered living S bacteria from the dead mice.
S strain → inject into mice → Mice live
(heat-killed)
S strain
(heat-killed)
+ → inject into mice → Mice die
R strain
(live)