Question

3'-ATGCTA-5' ... (A)
5'-TACGAT-3' ... (B)
In a hypothetical sequence of above given dsDNA if promoter is present at 5' of (A) strand and this DNA is involved in transcription, then what will be the correct sequence of mRNA ?

• A. 3'-AUCGUA-5'
• B. 3'-UAGCAU-5'
• C. 5'-UACGAU-3'
• D. 5'-AUCGUA-3'

Answer 1

The correct option is D 5'-AUCGUA-3'

Since, promoter is on strand a, so strand A will act as coding strand and strand B will act as template strand. In the question, we can say that the coding strand (of the DNA) and the RNA sequence so transcribed are similar, but not identical (RNA would code Uracil instead of Thymine).

During transcription (elongation) , RNA polymerase "walks" along one strand of DNA, known as the template strand, in the 3' to 5' direction. For each nucleotide in the template, RNA polymerase adds a matching (complementary) RNA nucleotide to the 3' end of the RNA strand.

So, the correct answer is " 5-AUCGUA-3' "