NEET Botany Molecular Basis of Inheritance Questions Solved


(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

                                                                                                                    = 1+1

Blending- As infection proceeds- the viral coats are removed from the bacteria by agitating in a blender 

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



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