The bacteriophage lambda genome can exist in either a linear form...

Question

The bacteriophage lambda genome can exist in either a linear form (see Figures 15.1 and 15.8) or a circular form.

Diagram the resulting fragments as they would appear on an agarose gel after electrophoresis.

Accepted Answer

Hi, everyone. Let's take a look at this practice problem together. Why would the resulting fragments appear in a single band on the Agarose gel? After electrophoresis of a circular lambda phage win digested with a restriction enzyme. Now let's go ahead and go through each of the answer options and discuss them individually as to why they are or are not the correct answer. Option. A states circular lambda phage has only one strand of DNA which results in a single band. So we should immediately be able to eliminate. Option A, we know that lambda age has two strands of DNA. So option A is incorrect. Option B states the circular structure of lambda phage ensures that the DNA fragments are all of the same size due to the action of the restriction enzyme resulting in a single band. So when the restriction enzyme cleaves DNA, it does. So at specific recognition sequences that it will recognize the circular structure of lambda age does not influence the cleavage sites of the restriction enzyme. So we can also eliminate. Option B, option D states, the circular shape of the lambda phage ensures that the DNA fragments have the same charge resulting in a single band. Now recall that DNA has the phospho dier backbone. So all DNA has the phospho dier backbone and that makes the DNA negatively charged, not the circular shape of the lambda phage. And furthermore, it is the size of the DNA fragments that are put through gel electrophoresis that determine the different bands produced, not the charge. So option D is also incorrect. The correct answer is option C now, when a lambda age is cut as a single location by a restriction enzyme, it will produce a single linear DNA molecule and it will always be the same fragment size, thus producing the single band on Agro gel. So the correct answer is option C circular lambda age can only be cut by restriction enzymes in one location resulting in a single band. All right, everyone. I hope you found this helpful and I'll see you soon for the next practice problem.

The bacteriophage lambda genome can exist in either a linear form (see Figures 15.1 and 15.8) or a circular form. Diagram the resulting fragments as they would appear on an agarose gel after electrophoresis.

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