They raised 2 types of bacteriophages
On radioactive phosphorous (32P)
On radioactive sulphur (35S).
35S gets into protein and 32P into DNA When both bacteriophages infected bacteria differently and by shaking them, viral protein coat was separated
After raising these bacteria it was found that those infected with 32P bacteriophage → radioactivity was found. But with 35S → no radioactivity was found.