Answer :
To answer this question, we need to consider the experiments that demonstrated DNA as the genetic material, particularly the famous experiment by Avery, MacLeod, and McCarty in the early 1940s that built upon Griffith's bacterial transformation experiments.
Background:
Griffith discovered that a non-virulent strain of bacteria (R strain) could be transformed into a virulent strain (S strain) when mixed with heat-killed virulent bacteria. This suggested a 'transforming principle' responsible for transferring virulence. Avery and his colleagues aimed to identify the nature of this transforming principle, eventually demonstrating that DNA was the genetic material transfusing the transformation.
Experiment:
Avery, MacLeod, and McCarty performed a series of experiments to identify the transforming substance:
Bacterial Transformation: They replicated Griffith's experiment but included various enzymes to degrade different potential molecules (DNA, RNA, and proteins) to see which would inhibit transformation.
Use of Enzymes:
- Enzymes that break down proteins (proteases), RNA (RNases), and DNA (DNases) were used.
- When the protein hydrolyzing enzyme (protease) was used, transformation still occurred, indicating proteins were not the transforming substance.
- It was the enzymatic destruction of DNA (with DNase) that prevented the transformation, confirming DNA as the genetic material.
Conclusion:
Therefore, if a protein hydrolyzing enzyme was used during an experiment:
- Proteins would be broken down, but transformation would still occur because the genetic material (DNA) is intact. Thus, the non-virulent R strain can be transformed into the virulent S strain.
Given the question, the correct choice would be:
D) The bacterial strain (R) was transformed into the bacterial strain (S).
This outcome aligns with the fact that a protein hydrolyzing enzyme would not hinder DNA's ability to effect transformation.
