Question

After viruses infect cells, the empty virions stay attached to the infected cells. Hershey and Chase used a blender to separate empty virion particles from the cells. Why was this important? What would have been the result if they hadn’t done this?

a. Many proteins are post-translationally modified with the addition of a phosphate. Could this have affected Hershey and Chase’s experiment? How

b. What other weakness may the Hershey Chase experiment have?

Answer 1

Hershey and Chase experiment used to find the genetic materia is protein or DNA. They used radioactive phosphorus for DNA and radioactive sulfur for protein.

Phage protein coat conatin radioactive sulphur it not enter into the bacteria it attached to the infected cell. The only radioactive phosphorous DNA of virus enter into the bacteria and tranformed with bacterial genome. We need to do blender to remove the Phage protein coat conatin radioactive sulphur in bacteria. After centrifugation the supernant contain the radioactive sulphur clearly shows the protein is not the genetic material. In another experiment the
radioactive phosphorus present inside the cell so the supernant is non radioactive it clearly tells the DNA enter into the bacterial cells and it must be genetic material.

If not blender means the phage cpat still attach to the bacteria after centrigugation the supernant has no radioactivity in both the experiment. So we not able to come any conclusion.

A. Yes post translation modification is the addition or removal of phospahte group in the protein structure. During post translation modification the radiolabel phosphate has a chance to addition to the protein coat. So the protein coat also have the radiolabel phosphorous some times leads to false result.

B. Not only DNA even RNA can binds with radiolabelled phosphorous. So why not RNA can become a genetic material in the bacyteria.