I am confused. If RNA transcription always grows from the 5' end to the 3' end, what does the direction of the promoter do for the mRNA transcribed?

From what i understand the RNA polymerase always extends the mRNA from the 5' end to the 3' end. Yet promoter sequences define the direction of transcription?

Which one is correct? Does mRNA transcription always extend from 5' to 3'? Or does the promoter dictate the direction in which the RNA polymerase extends mRNA?

Or it the truth somewhere in between?

  • 2
    $\begingroup$ Can you explain your thinking a bit further to focus the problem? $\endgroup$
    – Bryan Krause
    Dec 12, 2022 at 14:23
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    $\begingroup$ Think! DNA is double-stranded. What exactly do you understand in molecular terms by the statement "(the) promoter sequences define the direction of transcription"? Draw yourself a diagram. $\endgroup$
    – David
    Dec 13, 2022 at 14:33
  • $\begingroup$ Ok Sir, so there are 2 strands of DNA, so depending on the direction of the promoter, either one of the strands of DNA becomes the coding template (get transcribed)? Is that correct? $\endgroup$ Dec 15, 2022 at 2:22
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    $\begingroup$ I’ve just seen your comment. You need to address me as @david so I am alerted to your reply to me. (I don’t have to do the same as I am commenting on your post.) In answer to your query, that’s almost right. But it’s not only the DNA strand that is different, it’s its location or direction relative to that of the promoter. $\endgroup$
    – David
    Dec 22, 2022 at 19:22


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