The Hershey and Chase experiment could label phage DNA specifically using radioactive phosphorus because:

1. The bacteriophage infects the host bacterial cell by attaching to its surface, then injecting its nucleic acids inside. 2. The question was whether the injected material was DNA or protein. 3. Because phosphorous is found in DNA, but not protein, the DNA and not the protein would be tagged with radioactive phosphorus. 4. Sulfur was used the other way round, to tag protein specifically. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 14 'DNA Structure and Function', sections 14.1-14.6_