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Restriction enzyme reads a DNA strand containing nucleotide base pairs

  1. Mar 17, 2007 #1
    1. The problem statement, all variables and given/known data

    I know this is a biology question but this is the most busy forum so I decided to put it here:

    I'll make this simple. A restriction enzyme reads a DNA strand containing nucleotide base pairs. It cuts the strand after it reads a sequence of 6 base pairs - AAGCCT. Of course the probablity of the enzyme reading the correct base is 1/4. And it needs 6 of them.

    So what is the average length of a cut strand? I'm thinking you do (1/4)^6 and this will give you something.. but what?

    Thanks for your help in advance...

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 17, 2007 #2


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    Please put the questions on the correct forum. Our mods will just have to move it and theyre over worked as it is.:smile:
    Sorry can't help you with Biology. Thats also a problem, the biology people dont come here to answer bio questions.
    Last edited: Mar 17, 2007
  4. Mar 17, 2007 #3
    I'm more of a physics and math person than a bio person, but two questions: Is this DNA that's competely random? (from the math point of view), and the bigger question: Does it matter which end you're coming from? i.e. if you had a strand that was CCAAGGTCCGAATAGC, although AAGCCT doesn't appear from left to right, it does appear when going from right to left. (My bit of knowledge makes me believe it can work from both ends)
  5. Mar 18, 2007 #4


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    Okay, forget making it "simple." Can you give your problem exactly as it was given to you? What is the context? The length of a cut strand is the distance between the restriction sites, so there isn't enough information provided about what it is you're cutting to know that.

    Or, are you trying to find the probability of that exact 6 nucleotide sequence occuring more than once in a random sequence? Without being given any information about the length of the DNA strand, you have to assume they're talking about the distance between two restriction sites and not from a restriction site to the end of the DNA.

    So, please come back with some clarification of what the problem is, or we can't do much to help.
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