In Griffith's 1928 bacterial experiments, what concept did he demonstrate?

• A. A protein.
• B. A transforming principle that could transfer virulence from dead S strain to live R strain.
• C. An RNA molecule.
• D. A lipid.

Answer: (B)

Griffith’s work shows that heritable information can move from dead cells to living ones, changing their phenotype. He found that heat-killed, virulent S bacteria could still influence living R bacteria if mixed together: the R cells acquired the ability to produce a capsule and became virulent. This “transforming principle” carries information that can be taken up by another cell and used to make it resemble the donor, even though the donor cells are no longer alive. Over time, this principle was shown to be DNA, not a protein, RNA, or lipid, as the carrier of genetic information. So the key idea is that genetic material can be transferred between organisms, transforming their traits.