Final answer:
Radioactive phosphorus is used in DNA technologies to create DNA probes, which help in detecting specific DNA sequences by incorporating into the DNA's backbone and emitting a radioactive signal.
Step-by-step explanation:
The role of radioactive phosphorus in DNA technologies is primarily related to the creation of DNA probes. This is due to the presence of phosphorus in the backbone of the DNA molecule. Thus, radioactive phosphorus can be incorporated into the DNA during its synthesis. When DNA is labeled with radioactive phosphorus, scientists can use the radioactive signal to detect the presence and location of specific DNA sequences within a sample. This method is fundamental in various molecular biology techniques such as Southern blotting, where DNA fragments are transferred to a membrane and then probed using a complementary radioactive sequence to visualize specific DNA sequences of interest.