In 1952, Martha Chase worked to confirm that DNA, not protein, could independently carry the genetic material. Her team created bacteriophages with radiolabeled protein and bacteriophages with radiolabeled DNA. One group of phages contained radiolabeled sulfur, and another group contained radiolabeled phosphorus. Non-labeled bacteria were then infected with the phages. Following incubation, the material from inside the bacterial cell and the material that remained outside the bacteria were examined.
What was the theory behind the first step of this experimental design?