Step 1: Understanding the Concept:
Almost all cellular life stores its genetic information in DNA, but viruses are simpler and some of them use RNA instead as their genetic material. Whether a given virus is a "DNA virus" or an "RNA virus" is a fixed property of that virus group, not something that varies case by case.
Step 2: Key Approach:
One of the clearest pieces of evidence for RNA acting as genetic material came from reconstitution experiments on Tobacco Mosaic Virus, done by Fraenkel-Conrat and Singer. They pulled TMV apart into its separate protein coat and RNA core, then mixed the RNA of one TMV strain with the protein coat of a different strain.
Step 3: Detailed Explanation:
When this mixed, reconstituted particle infected a tobacco plant, the new virus particles produced carried the properties of the strain that donated the RNA, not the strain that donated the protein coat. This showed that the RNA, not the protein, carried the instructions passed to the next generation of virus, confirming RNA as TMV's genetic material. Adenovirus, pox virus, and herpes virus are all well-established DNA viruses; none of them were the subject of this classic RNA-inheritance experiment, and none use RNA as their genetic material.
Step 4: Final Answer:
The reconstitution experiment on Tobacco Mosaic Virus is what confirmed RNA as its genetic material, so option 2 is correct.