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Molecular Basis of Inheritance — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYMolecular Basis of Inheritance5 Marks
Question
Explain the process of transcription in a prokaryote.
OR
Describe the process of transcription in a bacterium.
✓

Answer

  1. Transcription unit in a bacterium consists of a promoter, structural genes, terminator and the enzyme DNA-dependent RNA-Polymerase.
  2. In bacteria, there is a single RNA polymerase, which catalyses transcription of all the three types of RNAs (mRNA, tRNA and rRNA).
  3. It binds transiently with the initiation factor (sigma factor), binds to the promoter and initiates transcription.
  4. It also facilitates opening of the double helical DNA and only the DNA strand with 3' → 5' polarity is transcribed, as the enzyme can polymerise the nucleotides only in 5' → 3' direction; it catalyses elongation using the ribonucleotides.
  5. Once the polymerase reaches the terminator sequence, it associates with the termination factor and the nascent RNA falls off and termination of transcription occurs.

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