Question

To estimate the number of cleavage sites in a particular piece of DNA with a known size, you can apply the formula N/4ⁿ where N is the number of base pairs in the target DNA and n is the number of bases in the recognition sequence of the restriction enzyme. If the recognition sequence for BamHI is GGATCC and the phage DNA contains approximately 48,500 bp, how many cleavage sites would you expect?

Accepted Answer

Hi, everybody. Let's take a look at this practice problem together. What will the total number of cleavage sites in 38,400 base pair long D N A which is digested by the enzyme A L U L. The recognition sequence for A L U L is A G C T. Assume that all four nucleotides are present in equal proportions is the answer. A 50 B 100 C 150 or D 200 from the information in the question, we should deduce that the enzyme Aloul is a restriction enzyme. How do we know that recall that a restriction enzyme recognizes specific sequences and cleaves at those sites? This is what the enzyme A L U L does. Therefore, how do we calculate the total number of cleavage sites? You will need to know a formula in order to answer this question. And that formula is the following where the total number of cleavage sites Is equal to capital N divided by 4 to the little end power. Now capital N stands for the number of base pairs in the D N A sequence. Little N is the number of bases in the recognition sequence. So let's solve our formula here. We have big N over four to the little power. Capital N is the length of base pair or the number of base pairs in DNA which is 38, divided by four to the little power. Now, our recognition sequence recall is a G C T which means that there are four bases in the recognition sequence. Therefore, we will have four to the 4th power Solving this equation. We have 38,400 divided by 256 equals 150. Therefore, the correct answer will be option C- 150. Alright, everybody, I hope you found this helpful and I'll see you soon for the next practice problem.

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