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Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance1 Mark
Question
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.
  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
Assertion: Core enzyme catalyses chain elongation of RNA.
Reason: The presence of sigma factor is required for initiation of transcription.
✓

Answer

  1. Both assertion and reason are true, but reason is not the correct explanation of assertion.

Explanation:

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 RNA chain - initiation event, sigma is released and the core enzyme catalyses chain elongation.

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