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Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance1 Mark
MCQ
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: $R-$type of Pneumococcus is non$-$virulent.
Reason: $R-$type of Pneumococcus can be virulent by having transformation with $S -$type of Pneumococcus.
  • A
    Both assertion and reason are true, and reason is the correct explanation of assertion.
  • ✓
    Both assertion and reason are true, but reason is not the correct explanation of assertion.
  • C
    Assertion is true, but reason is false.
  • D
    Both assertion and reason are false.
✓

Answer

Correct option: B.
Both assertion and reason are true, but reason is not the correct explanation of assertion.
Transformation is the change in the genetic constitution of an organism by picking up genes present in the environment. Pneurnococcus has two strains $-$virulent $(S)$ and non$-$virulent $(R).$ The virulent strain causes pneumonia. $R-$type bacteria form irregular or rough colonies and did not produce any disease while the $S-$type bacteria cause pneumonia and then death in the mice. Griffith injected a combination of live $R-$type and heat killed $S-$type bacteria into mice. While some mice survived, others developed the disease of pneumonia and died. Autopsy of the dead mice showed that they possessed both the types of bacteria in living state, though the mice had been injected with dead virulent and living non$-$virulent bacteria. The occurrence of living $S-$type virulent bacteria is possible only by their formation from $R-$type non$-$virulent bacteria, which pick up the trait of virulence from dead bacteria. The phenomenon is called transformation.

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