Hershey and Chase carried a series of experiments to show that DNA (deoxyribonucleic acid) is the genetic material. Earlier biologists believed that proteins are the genetic material. In this experiment, a bacteriophage T2 phage was used to infect a bacterium. The phage DNA was labeled with radioactive phosphorus-32 ( 32 P), and the phage protein was labeled with radioactive sulfur-35 ( 35 S). The amount of radioactive isotopes was observed in the infected bacterium.

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Chapter 14, Problem 2TYK

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Hershey and Chase carried a series of experiments to show that DNA (deoxyribonucleic acid) is the genetic material. Earlier biologists believed that proteins are the genetic material. In this experiment, a bacteriophage T2 phage was used to infect a bacterium. The phage DNA was labeled with radioactive phosphorus-32 (³²P), and the phage protein was labeled with radioactive sulfur-35 (³⁵S). The amount of radioactive isotopes was observed in the infected bacterium.

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If a researcher accidentally transformed the bacterial two hybrid plasmids ( pKT25-X and pUT18-Y) into a normal strain of E coli that produces adenylate cyclase, his/her experiment will: a. show a high lacZ activity in all tubes (control and experiment) because Proteins X and Y do not need to be interacting in order to activate lacZ gene prescription. b. not work because cells lack cAMP. c. need replicates in order to show true interaction between X and Y.

In Hershey-Chase experiment, bacteriophages protein coats were tagged with radioactive isotope S-32. These phages were used to infect E. coli cells and the cells were further centrifuged to form pellets. Why was the radioactivity level of S-32 found greater outside the cells compared to the E. coli cell pellets? Explain briefly. If the experiment is repeated in the same manner but this time the phage protein coats are labelled with isotope X and the phage DNA with isotope Y, which isotope’s radioactivity will be found in greater amounts in the E. coli cell pellets after centrifugation? Explain briefly.

What observation led Hershey and Chase to the conclusion that DNA, not the protein coat, carried the genetic information needed to make new virus or phage particles? Select one: a. The cell membrane of the bacteria infected with a virus tagged with radioactive phosphorus exhibited radioactivity after it’s initial cell division. b. Bacterial cells infected with viruses tagged with radioactive phosphorus were radioactive, indicating viral DNA entered the host cell. c. The cell was vigorously shaken, causing the protein coats to detach from the cell membrane of the bacteria. The protein coats contain genetic information. d. Bacterial cells infected with viruses tagged with radioactive sulfur were radioactive, indicating viral protein entered the host cell.