What experiment did Frederick Griffith conduct to discover transformation?

Frederick Griffith's experiment aimed to investigate the phenomenon of transformation, where genetic material from one organism could be taken up by another organism, leading to a change in its phenotype. In his pivotal study, he used two strains of the bacterium Streptococcus pneumoniae: the virulent S strain (which has a smooth capsule and causes disease) and the non-virulent R strain (which has a rough appearance and does not cause disease).

By injecting mice with heat-killed S cells alongside living R cells, Griffith discovered that the R cells were transformed into virulent S cells. This unexpected outcome demonstrated that some "transforming principle" from the heat-killed S cells was taken up by the living R cells, leading to their transformation into a pathogenic form. This experiment provided foundational evidence for the understanding of genetic material and paved the way for later discoveries regarding DNA.

The correct selection illustrates how Griffith was able to prove the transfer of genetic information between the two strains under specific experimental conditions, highlighting the significance of transformation in microbiology and genetics.