The electrophoresis gel shown in part (a) is from a DNase I footp...

Question

The electrophoresis gel shown in part (a) is from a DNase I footprint analysis of an operon transcription control region. DNA sequence analysis of a 35-bp region is shown in part (b). The control region, labeled with ³²P at one end, is shown in a map in part (c). Separate samples of control-region DNA are exposed to DNase I, and the resulting DNase I–digested DNA is run in separate lanes of the electrophoresis gel. Unprotected DNA is in lane 1, DNA protected by repressor protein is in lane 2, and RNA polymerase–protected DNA is in lane 3. The numbers along the electrophoresis gel correspond to the 35-bp sequence labeled on the map in part (c). Use the information provided to solve the following problems.

Determine the DNA sequence of the 35-bp region examined.

Accepted Answer

Welcome back, everyone. Let's look at our next problem. Researchers are interested in studying the interactions between a transcription factor and a specific DNA sequence in a gene promoter. They decide to use DNA S foot printing DNA S one ft printing, excuse me, to identify the binding site of the transcription factor in the DNA sequence, which of the following statements accurately describes the technique of DNA S one ft printing and its application in this study. So let's think about we're going to look through our answer choices in a moment. But let's just briefly think about the basics of DNA S one ft printing and it involves digesting a DNA segment with the restriction enzyme DNA S one which cleaves it into many, many different bands. But in regions where a protein is bound to the DNA DNA S one cannot. So when you run these fragments, after you cut up your sequence with the enzyme, and you run these fragments on a gel, you're going to see distinct larger bands that were not cut with DNA S one where that DNA was protected by the protein. So with that sort of basic in mind, let's look through our answer choices, looking for the correct description of the technique and how you would apply it in this study where again, scientists are looking for a transcription factor and a specific DNA sequence in a gene promoter. So presumably the transcription factor will be bound to that promoter. So let's start with choice. A DNA S one is used to transcribe the DNA sequence which is then analyzed by gel electrophoresis to identify the binding site of the transcription factor. Well, the purpose is correct, you're wanting to identify the binding site. But the technique is not DNA S one is used to cleave the DNA sequence not to transcribe it. So choice A is incorrect. Choice. B says DNA S one is used to cleave the DNA sequence into fragments which are then analyzed by gel electrophoresis to identify the binding site of the transcription factor. And this is a correct description both of the technique and how it's being applied in this circumstance. But we're going to be thorough. So we'll keep looking at our other answer. Choices. Troy C says DNA S one is used to amplify the DNA sequence which is then analyzed by gel electrophoresis to identify the binding side of the transcription factor. Well, DNA S one as we saw is used to cleave the DNA sequence. It's PC R which is the technique that you use to amplify a DNA sequence. So choice C is not correct and finally choice D DNA S one is used to digest the transcription factor, which is then analyzed by gel electrophoresis to identify its binding site in the DNA sequence. And in this, we have the correct purpose to identify the binding site. But DNA swan is used to cleave DNA, not digest that protein. So that's why choice D is not correct. So again, we're looking for if you're looking for a specific binding site, and you're using DNA S foot printing to identify it, what statement accurately describes the technique of DNA S one ft printing and its application. In this example, choice B DNA S one is used to cleave the DNA sequence into fragments which are then analyzed by gel electrophoresis to identify the binding site of the transcription factor. See you in the next video.

Key Concepts

DNase I Footprint Analysis

Electrophoresis

Operon and Transcription Control

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