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Transcription

Discussion in 'Science' started by BelleDuJour, Feb 24, 2012.

  1. BelleDuJour

    BelleDuJour Star commenter

    I prefer to say a coding strand and a template strand. Temmplate strand is complementary to the coding strand and it is the coding strand where mRNA forms.
    So, if the coding strand says ACG the template strand will say TGC and mRNA will be UCG.
    In the case of your question, I think they are asking for the base sequence on the template strand.
    Re-read the question. I think the question is, in fact, asking for the template strand code.
     
  2. "Give the DNA base sequence that codes for threonine."

    this is what they say
     
  3. BelleDuJour

    BelleDuJour Star commenter

    I am confused now!
    Will give it another ponder!
     
  4. There are actually four RNA codons that code for threonine, ACU, ACC, ACA and ACG. This means then that on the sense (5' to 3') DNA strant this would then be ACT, ACC, ACA and ACG. mRNA is actually synthesized using the antisense strand of DNA (3' to 5') as the template.and therefore the possible DNA sequences for Threonine would be TGA, TGG, TGT and TGC. There is also the issue of codon bias which of course will be different for each species.
     
  5. gjeh67

    gjeh67 New commenter

    Have any of the other posters looked at the actual question you refer to?
    The question gives the mRNA codon as ACC since this pairs with the DNA sequence that codes for the mRNA using simple base pairing A-T & G-C the DNA sequence must be TGG (which you say is indeed the correct answer).
    There is no need to over-think or over-complicate the answer by reference to sense/antisense or coding/non-coding strands. These may be interesting biological principles but not at all relevant to the question actually being asked on the paper.
    Have you possibly also got a bit mixed up with your mRNA codons and your tRNA anti-codons?
    A valuable lesson for your students too I think.
     
  6. BelleDuJour

    BelleDuJour Star commenter

    I had mis-read the question!
    Had another ponder and came up with exactly what you have said which is:
    ..........because, of course, the mRNA is complementary to the DNA code!

     
  7. In reference to gjeh67 then if the OP were more clear as to the link to the question then that would have been fine. However the post was not specific and, pedantic as it is, was therefore unclear, and so ambiguous. The distinction between sense/antisense at AS/A2 is vital as is the distinction between mRNA and tRNA codons and anti-codons..
     
  8. ScienceGuy

    ScienceGuy Occasional commenter

    I would disagree with this - I teach transcription at A level and have never used sense / antisense when teaching this topic. That may be due to the specification of course.
     

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