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Transcription in DNA

  1. Nov 17, 2014 #1

    Maylis

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    Gold Member

    Hello,

    How is it that transcription occurs on the non-coding strand? If you are to code for proteins, wouldn't it want to do the transcription on the coding strand? This is puzzling me
     
  2. jcsd
  3. Nov 17, 2014 #2

    jedishrfu

    Staff: Mentor

  4. Nov 19, 2014 #3

    Maylis

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    I think I get it now. So, it will base pair with the non-coding strand so that it has an identical copy of the coding strand. It would be useless to create a copy of a non-coding strand, since a non-coding strand is "inert" so to speak and won't be functional. I know that is vague terms but not sure exactly the right way to say it.
     
  5. Nov 27, 2014 #4
    The way I learned it in my Biology course was by referring to the strands as complementary and template strands. The template strand is the non-coding strand - template is a more intuitive way of thinking of it (for me, anyway). The complementary strand has a base sequence that is complementary to the RNA sequence, and to the template strand, hence the name.

    I personally find this easier to use, however, if this is used and words like coding and non-coding strands are required, you would have to take care when "translating" the terms to what is expected of you.
     
  6. Nov 27, 2014 #5

    Ygggdrasil

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    The template strand is complementary to the mRNA sequence because RNA polymerase synthesizes a RNA complementary to its template. Thus, the non-template strand (which is complementary to the template strand) has a sequence identical to the mRNA (except for the replacement of Ts for Us).
     
  7. Nov 28, 2014 #6
    The definitions are ultimately arbitrary. Coding sequence is defined as that of the mRNA, which is the reverse complement of the DNA strand which was read and transcribed by RNA polymerase, so by definition the physical strand of DNA read is the non-coding strand. For simplicity's sake, we usually look at the DNA strand sequence which is the same as the mRNA for information content, even though that is not the strand that is physically read by the polymerase.
     
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