What happened when heat-killed S cells along with R cells were injected into mice in Griffith's experiment?

Mice died and showed live S cells in the blood

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)