DBQ DP Biology Is DNA the Hereditary Material? A virus is a non-living particle composed of a piece of DNA enclosed by a protein coat. Once attached to the surface of a cell by its tail fibers, the virus contracts its sheath and injects its DNA into the cell, leaving the protein coat behind. Protein coat Collar Contractile Sheath Tail fibers An experiment was conducted to determine whether it was protein or DNA which was the hereditary material. The experimenters, known as Hershey and Chase, grew some viruses in nutrient medium with radioactive phosphorus. They grew another set of viruses in nutrient medium with radioactive sulfur. Hershey and Chase knew that DNA contained phosphorus, but protein did not, while protein contained sulfur which DNA did not. In other words, they had two batches of viruses, one batch with radioactive DNA (Batch A) and another batch with radioactive protein (Batch B). Separate cultures of the bacterium Escherichia coli were infected with either the A or B type viruses. After sufficient time for DNA injection had passed, the empty phage “ghosts” were separated from the bacterial cells, and the two parts were tested for radioactivity. In a second experiment, the phages were allowed to complete their life cycle and the offspring were tested for radioactivity. The results are presented below: Phage Type Bacterial Fraction Phage Fraction Phage Offspring A (32P) radioactive non-radioactive radioactive B (35S) non-radioactive radioactive non-radioactive 1) What do these results suggest happened to the DNA in “type A” viruses? 2) Why were the offspring of “Type A” phages radioactive while the offspring of “Type B” viruses were not? 3) If protein and not DNA were the information carrier in viruses, predict the results Hershey and Chase would have obtained. The life cycle of a virus is given below. By the way, Alfred Hershey and Martha Chase performed their experiment in 1952.