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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: Core enzyme catalyses chain elongation of $\text{RNA}.$
Reason: The presence of sigma factor is required for initiation of transcription.
  • 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.
The core' enzyme which catalyses covalent chain extension, consists of two $\alpha$ polypeptides $($each of molecular weight about $41,000),$ one $\beta$ polypeptide $($molecular weight about $155,000)$ one $\beta-$ polypeptide $($molecular weight about $165,000)$ and one $\omega-$co$-$polypeptide $($molecular weight about $12,000).$ The holoenzyme contains in addition, $\alpha-$polypeptide $($molecular weight about $95,000).$ The presence of the sigma factor is required for initiation at the proper transcription initiation $($or promoter$)$ sites. After each $\text{RNA}$ chain $-$ initiation event, sigma is released and the core enzyme catalyses chain elongation.

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