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AQA June 2011 A2 Biology Help

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    Im stuck on the whole of question 5
    QP: http://filestore.aqa.org.uk/subjects...W-QP-JUN11.PDF
    MS: http://filestore.aqa.org.uk/subjects...W-MS-JUN11.PDF

    Im not asking for someone to just look at the ms, I need to understand whats going on because I know the content, but the question is not ringing any bells. Thanks

    You are not alone, all our teachers skipped restriction mapping and so I was also confused when I came to this question and then my teacher explained it to me

    Firstly for question 5ai, To get two fragments from that whole plasmid (with the unknown DNA), there would have to be two cuts as one cut would just make it a single linear strand. So, since there is only one recognition site on the plasmid (for the restriction endonuclease we are using), there must be another on the unknown DNA and So the answer is there is ONE RECOGNITION SITE ON THE UNKNOW DNA FOR Kpn1. The third marking point on the markscheme refers to the fact that two fragments are produced, one of these are 1000 base pairs. Since we know that the plasmid is 3000 base pairs along, this must be the smaller fragement between the two recognition sites. So there is a gap of 1000 base pairs between the two restriction sites for there to be a cut there to produce a fragment of 1000 base pairs

    For part 5 a ii) leading on from this idea, other fragment would be larger, considering the fact that the plasmid along is 3000 base pairs. So this very large fragment would be made of the rest of the plasmid and the unknown DNA.
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