Bacteriophages are viruses that infect bacteria. In an experiment, bacteriophages were labeled with either radioactive phosphorus or radioactive sulfur. The labeled bacteriophages were incubated with bacteria for a brief amount of time and then removed. The infected bacteria cells were found to contain significant amounts of radioactive phosphorus but not radioactive sulfur. Based on the results of the experiment, which of the following types of molecules did the bacteriophages most likely inject into the bacteria cells? (A) Simple carbohydrate (B) Amino acid (C) DNA (D) Polypeptide Unauthorized copying or reuse of any part of this page is illegal. GO ON TO THE NEXT PAGE. -9

This experiment shows that when bacteriophage infects bacteria, it only inserts its DNA (radioactive phosphorus is incorporated only in nucleic acid, while radioactive sulfur is incorporated only in proteins). Proteins with incorporated sulfur are located within the capsid of bacteriophage, which stays outside the bacterial cell.

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