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Homework Help: How to solve restriction mapping problems?

  1. Nov 16, 2016 #1
    1. The problem statement, all variables and given/known data
    A piece of linear DNA 1000bp long is completely digested by four enzymes, E, B, P, and S.
    We are given the sizes of fragments (in bp) produced when each of the enzymes are used in isolation, and when they are used in different combinations:
    E : 227, 773
    B : 150, 450, 400
    P : 400, 600
    S : 206, 794
    E + B : 223, 227, 400, 150
    E + P : 227, 373, 400
    B + S : 56, 150, 344, 450
    P + S : 194, 206, 600

    2. Relevant equations
    Not applicable

    3. The attempt at a solution

    I understand that with E + B, for example, as 227, 400, and 150 bp are present, enzyme B must have cut the 773 fragment into three pieces, 223, 400, and 150. I really don't know how to piece this information together to make a restriction map, it doesn't make any sense to me.
    Last edited by a moderator: Jan 18, 2018
  2. jcsd
  3. Nov 16, 2016 #2


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    Hello foldy, :welcome:

    The problem statement is missing a question. Could it be it's incomplete ?
    You seem to know what a restriction map is; could you elucidate ?

    In the mean time I notice E+B has no 450 base-pair sized chunks. Could that be the consequence of one of the restrictions ?
  4. Nov 16, 2016 #3
    Thanks for your reply!
    Yes, apologies for that, there isn't a question as such; I need to construct a restriction map from this data. My question is how do I do this?
    A restriction map shows all the positions of the restriction sites in a piece of DNA, which has information such as the length of the fragments and the enzyme responsible for each restriction site.
    Yes, I think that with the E + B combination, enzyme E must have cut into the 450 fragment, dividing it into 227 bp and 223 bp. I'm just not sure how to go from recognising points such as these to constructing the full restriction map.
  5. Nov 16, 2016 #4


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    Can you try drawing the different possible maps that are consistent with the E, B, and E+B digests? After you have those possibilities, consider the other two restriction enzymes and use those data to try ruling out some of the maps.
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