Which molecule did Avery, MacLeod, and McCarty identify as the transforming principle in their 1944 experiments?

Which molecule did Avery, MacLeod, and McCarty identify as the transforming principle in their 1944 experiments?

• A. RNA.
• B. Protein.
• C. DNA.
• D. Lipids.

Answer: (C)

The main idea being tested is what substance carried genetic information in transformation experiments. Avery, MacLeod, and McCarty showed that DNA is the transforming principle because only treating the virulent-strain extract with DNase—the enzyme that digests DNA—eliminated its ability to convert nonvirulent cells into virulent ones. When proteins or RNA were degraded by their respective enzymes, transformation still occurred, indicating those molecules were not the carriers. This demonstrated that the genetic material responsible for transferring traits between cells is DNA, a foundational shift in our understanding of heredity and molecular biology.

The main idea being tested is what substance carried genetic information in transformation experiments. Avery, MacLeod, and McCarty showed that DNA is the transforming principle because only treating the virulent-strain extract with DNase—the enzyme that digests DNA—eliminated its ability to convert nonvirulent cells into virulent ones. When proteins or RNA were degraded by their respective enzymes, transformation still occurred, indicating those molecules were not the carriers. This demonstrated that the genetic material responsible for transferring traits between cells is DNA, a foundational shift in our understanding of heredity and molecular biology.