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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: Same $\text{tRNA}$ can recognise more than one codons differing only at the third position.
Reason : The specificity of a codon is particularly determined by the first two bases.
  • ✓
    Both assertion and reason are true, and reason is the correct explanation of assertion.
  • B
    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: A.
Both assertion and reason are true, and reason is the correct explanation of assertion.
It has been sh own, for instance that the same $\text{tRNA}$ can recognise more than one codons differing only at the third position. This pairing is not very stable and is allowed due to wobbling in base pairing at this third position. This kind of wobbling allows economy of the number of $\text{tRNA}$ molecules, since several codons meant for same amino acid are recognised by same $\text{tRNA}$. For instance, anticodon $\text{CGC}$ can recognise codons $\text{GCU, GCC}$ and $\text{GCA.}$

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