(a)Hershey and Chase carried their experiment in three steps : infection, blending, centrifugation. Explain each step.
(b)Write the conclusion and interpretation of the result they obtained. 5mark
(a)Infection - Radioactive phosphorus / phosphorus labelled bacteriophages were allowed to infect E.coli - growing in a culture medium,simultaneously radioactive sulphur / sulphur labelled bacteriophage was allowed to infect E.coli growing in another culture medium
Blending- As infection proceeds- the viral coats are removed from the bacteria by agitating in a blender =½
Centrifugation - virus particles were seperated from bacteria by spinning them in a centrifuge= ½
(b)Conclusion - DNA is the genetic material = 1
Interpretation - sulphur labelled viral protein did not enter the bacteria during infection , whereas phosphorus labelled viral DNA entered into the bacteria to cause infection = ½ + ½