Skill check: DNA discovery and structure

Alfred Hershey and Martha Chase used phages (viruses that infect bacteria) to determine whether DNA or protein was the genetic material. Phages consist of DNA inside a protein coat, and they inject their genetic material into bacterial cells, "reprogramming" them to make more phage.

In their experiment, Hershey and Chase used radioactive sulfur (

^{35} S

) to label phage proteins and radioactive phosphorous (

^{32} P

) to label phage DNA. They infected bacterial cultures with each set of phages, then spun the cultures at high speed to separate the phages and bacteria.

Hershey and Chase found

^{32} P

in the pellet (lump of bacteria at the bottom of the tube), but

^{35} S

only in the liquid above the pellet. This result told them that DNA had been injected into the bacteria and was the genetic material.

What would the result of Hershey and Chase’s experiment have been if protein (and not DNA) were actually the genetic material?

(Choice A)
Since the phages would have injected their proteins into the bacteria, radioactive sulfur would have been found in the pellet.
(Choice B)
Since the phages would have injected their DNA into the bacteria, radioactive phosphorous would have been found in the pellet.
(Choice C)
Since no phage DNA would have entered the bacteria, radioactive phosphorous would have been found only in the liquid above the pellet.
(Choice D)
Neither radioactive sulfur nor phosphorous would have been found in the pellet, since the phages could not have entered the bacteria.

HS biology (archived)

Course: HS biology (archived) > Unit 16

Problem