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    Hope somebody can clear this up??

    In transcription the RNA polymerase unzips a segment of the DNA and then moves along one of the strands to form the pre-mrna...

    So does the mRNA move down the unzipped segment and then back again - or does it do the unzipping and polymerisation at the same time?
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    (Original post by Cyanohydrin)
    Hope somebody can clear this up??

    In transcription the RNA polymerase unzips a segment of the DNA and then moves along one of the strands to form the pre-mrna...

    So does the mRNA move down the unzipped segment and then back again - or does it do the unzipping and polymerisation at the same time?
    DNA helicase does the DNA unzipping by breaking H bonds between nucleotides.
    The mRNA polymerase binds to a promoter site upstream of the sequence for replication, mRNA nucleotides line up along the 'unzipped' DNA strand (the antisense strand) via complementary base pairing forming H-bonds, the RNA polymerase form the phosphodiester bonds between the mRNA nucleotides.
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    Can someone please confirm for me that pages 86-87 in the CGP revision guide aren't really relevant to the spec?


    No mention of the diagnosis/treatment etc stuff in the specc as far as I can see and I don't remember us being taught about it, but don't want to miss it if it is required.
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    (Original post by Tericon)
    Can someone please confirm for me that pages 86-87 in the CGP revision guide aren't really relevant to the spec?


    No mention of the diagnosis/treatment etc stuff in the specc as far as I can see and I don't remember us being taught about it, but don't want to miss it if it is required.
    i havnt bothered with them, i think its just common sense that people with cancer in the family are more prone so should get screened earlier and that
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    (Original post by sammycjones)
    i havnt bothered with them, i think its just common sense that people with cancer in the family are more prone so should get screened earlier and that
    Thanks, I only didn't bother because I didn't want to tackle that horrific 25 marker at the bottom of the page
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    (Original post by indifferencepersonified)
    DNA helicase does the DNA unzipping by breaking H bonds between nucleotides.
    The mRNA polymerase binds to a promoter site upstream of the sequence for replication, mRNA nucleotides line up along the 'unzipped' DNA strand (the antisense strand) via complementary base pairing forming H-bonds, the RNA polymerase form the phosphodiester bonds between the mRNA nucleotides.
    I did a TSR search for that and it came up with this thread http://www.thestudentroom.co.uk/show....php?t=1601159 :holmes: which seems to conclude rna polymerase does the unzipping..
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    (Original post by Tericon)
    Thanks, I only didn't bother because I didn't want to tackle that horrific 25 marker at the bottom of the page
    you can tell how much i looked at them pages as i didnt even realise that 25 mark question was there! :P
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    (Original post by Cyanohydrin)
    I did a TSR search for that and it came up with this thread http://www.thestudentroom.co.uk/show....php?t=1601159 :holmes: which seems to conclude rna polymerase does the unzipping..
    I am CERTAIN that DNA Helicase does the unzipping.
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    (Original post by Get Real)
    I am CERTAIN that DNA Helicase does the unzipping.
    source??

    like this just says rna polymerase

    http://biology.about.com/od/cellular...nscription.htm
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    (Original post by Cyanohydrin)
    I did a TSR search for that and it came up with this thread http://www.thestudentroom.co.uk/show....php?t=1601159 :holmes: which seems to conclude rna polymerase does the unzipping..
    It says in NT, and I quote: 'The enzyme DNA helicase acts on a specific region on the DNA molecule to break the hydrogen bonds between the bases, causing the two strands to seperate and expose the nulceotide bases in that region'

    Also, have you never heard the rubbish biology joke: If I could be any enzyme I would be DNA helicase so i could unzip your genes. . .?
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    (Original post by indifferencepersonified)
    It says in NT, and I quote: 'The enzyme DNA helicase acts on a specific region on the DNA molecule to break the hydrogen bonds between the bases, causing the two strands to seperate and expose the nulceotide bases in that region'

    Also, have you never heard the rubbish biology joke: If I could be any enzyme I would be DNA helicase so i could unzip your genes. . .?
    Yes! But that is DNA replication, this is the synthesis of a specific but of pre-mRNA...

    I don't trust NT to be honest.
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    (Original post by Cyanohydrin)
    source??

    like this just says rna polymerase

    http://biology.about.com/od/cellular...nscription.htm
    " The enzyme DNA Helicase acts on a specific region of the DNA molecule to break the Hydrogen bonds between the bases, causing the two strands to seperate and expose the Nucleotide bases in that region " - Nelson Thorne Text Book.

    " Many cellular processes (DNA replication, transcription, translation, recombination, DNA repair, ribosome biogenesis) involve the separation of nucleic acid strands. Helicases are often utilized to separate strands of a DNA double helix or a self-annealed RNA molecule using the energy from ATP hydrolysis, a process characterized by the breaking of hydrogen bonds between annealed nucleotide bases. " - http://en.wikipedia.org/wiki/Helicase


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    (Original post by Jing_jing)
    Yeah, I can't wait till this one is over either, I have M2 on the same day, and M3 an STEP on Monday, and then STEP after the biology exam.

    Because AQA are sadists, discontent with merely setting hard questions, they've made it their mission to mess up people's revision timetables too
    if their mission was to mess up peoples revision timetable they have succeded at that aswel
    what will be their next mission cant think but im sure the wil think of something
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    (Original post by Cyanohydrin)
    Yes! But that is DNA replication, this is the synthesis of a specific but of pre-mRNA...

    I don't trust NT to be honest.
    I am pretty much certain (although will accept a reliable source as contradiction) that DNA helicase works in both.
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    (Original post by indifferencepersonified)
    I am pretty much certain (although will accept a reliable source as contradiction) that DNA helicase works in both.
    (Original post by Get Real)
    " The enzyme DNA Helicase acts on a specific region of the DNA molecule to break the Hydrogen bonds between the bases, causing the two strands to seperate and expose the Nucleotide bases in that region " - Nelson Thorne Text Book.

    " Many cellular processes (DNA replication, transcription, translation, recombination, DNA repair, ribosome biogenesis) involve the separation of nucleic acid strands. Helicases are often utilized to separate strands of a DNA double helix or a self-annealed RNA molecule using the energy from ATP hydrolysis, a process characterized by the breaking of hydrogen bonds between annealed nucleotide bases. " - http://en.wikipedia.org/wiki/Helicase


    http://users.rcn.com/jkimball.ma.ult...html#The_Steps

    Maybe DNA polymerase is a transcription factor?

    this animation makes no mention :holmes:

    http://highered.mcgraw-hill.com/site...scription.html

    you could be correct, I hope you are because it makes more sense in my head that way...
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    I think some RNA polymerases can contain two parts, which simultaneously unwind and transcribe the mRNA from the DNA; in the NT textbook it does say helicase does the unzipping though so I'd go with that
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    (Original post by l4ith)
    I think some RNA polymerases can contain two parts, which simultaneously unwind and transcribe the mRNA from the DNA; in the NT textbook it does say helicase does the unzipping though so I'd go with that
    That would make sense given the animations I have watched!

    Just to throw a spanner in the works.. this book...



    ..makes no mention of DNA polymerase - not that I think it will matter in the exam what you put regarding this issue..
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    (Original post by Cyanohydrin)
    That would make sense given the animations I have watched!

    Just to throw a spanner in the works.. this book...



    ..makes no mention of DNA polymerase - not that I think it will matter in the exam what you put regarding this issue..
    I can only assume that this DNA stuff is pretty recent, hence there seems to be contradictions from normally reliable sources - but I will be writing DNA Helicase, simply because the Text Book never lies
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    (Original post by Get Real)
    I can only assume that this DNA stuff is pretty recent, hence there seems to be contradictions from normally reliable sources - but I will be writing DNA Helicase, simply because the Text Book never lies
    but my textbook is written by Bill Inge the chief examiner

    I suspect it will just be a tick for unzips or something...
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    (Original post by Cyanohydrin)
    but my textbook is written by Bill Inge the chief examiner

    I suspect it will just be a tick for unzips or something...
    Why don't you go through mark schemes of transcription questions? They're pretty reliable.
 
 
 
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