In the Hershey-Chase experiment, which observation supported the conclusion that genetic material is DNA?

• A. Labeled protein entered the bacterial cells
• B. Labeled DNA stayed outside the cells
• C. The unlabeled DNA entered the cells
• D. Labeled DNA was found inside the bacterial cells

Answer: (D)

The main idea being tested is how we can tell what carries genetic information during a virus infection. The Hershey-Chase experiment labeled the phage’s DNA with a radioactive tag and the protein coat with a different tag, then watched where each tag ended up after the virus infected bacteria. The crucial finding was that the label on DNA was found inside the bacterial cells and in the newly formed phages, while the label on the protein coat did not enter the cells. This shows that the genetic material entering the host and directing the production of new viruses is DNA. If the protein label had been the one entering the cells, that would have pointed to protein carrying the genetic information, but that didn’t happen. So, the observation that labeled DNA is found inside the bacterial cells best supports DNA as the genetic material.