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NEETZoologyMolecular Basis of Inheritance

Observe the following short double-stranded DNA sequence of a transcription unit: Top strand: 3' -ATGCGTA- 5' Bottom strand: 5' -TACGCAT- 3' If the promoter is located at the left end of this sequence, what will be the sequence and polarity of the transcribed mRNA?

Options

  1. A5' -TACGCAT- 3'
  2. B3' -UACGCAU- 5'
  3. C5' -AUGCGUA- 3'
  4. D5' -UACGCAU- 3'

Correct answer

D. 5' -UACGCAU- 3'

Step-by-step solution

The promoter is located at the left end of the DNA sequence, meaning RNA polymerase binds there and moves towards the right. Since RNA synthesis occurs only in the 5' 3' direction, the enzyme must use the DNA strand with 3' 5' polarity (from left to right) as the template. Here, the top strand ( 3' -ATGCGTA- 5' ) has the correct 3' 5' polarity from left to right, making it the template strand. The bottom strand is the coding strand. The transcribed mRNA will be complementary to the template strand, with Uracil (U)

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