A. How long of a region of DNA is ?covered up? by the binding of RNA polymerase
ID: 40946 • Letter: A
Question
A. How long of a region of DNA is ?covered up? by the binding of RNA polymerase II and the transcription factors?
B. What banding pattern would you expect to see if you did not add TFIID?
13) In the DNA footprinting experiment shown here, a researcher began with a sample of cloned DNA 300 bp in length. This DNA contained a eukaryotic promoter for RNA polymerase II. For the sample loaded in lane 1, no proteins were added. For the sample loaded in lane 2, the 300-bp fragment was mixed with RNA polymerase II plus TFIID and TFIIB 2 300 bp- 250 bp 150 bp 75 bp How long of a region of DNA is "covered up" by the binding of RNA polymerase II and the transcription factors? What banding pattern would you expect to see if you did not add TFIID?Explanation / Answer
The TFIIB is the transcription factor that stabilizes the preinitiation complex during transcription when the RNA polymearse II binds to tht promoter (TATA box). The TFIID is the first initiation factor binds to RNA polymerase II at TATA box and later binding of TFIIB stabilizes this pre initiation complex.
A. The DNA is covered up between 10 to 35 bp with the binding of RNA polymerase II and transcription factors as the promoter TATA box is located between 10 and 35 bp sequences.
B. If TFIID is not added to DNA, the binding of RNA polymerase II to TATAbox and addition of TFIIB for stabilisation of pre initiation complex does not occur. The binding of RNA polymerase II to promoter may take place but not efficiently and binding of TFIIB does not take place because of the absence of TFIId and preinitiation complex is not formed and hence no transcription. Thus, the banding pattern observed would be binding of RNA polymerase II at TATA box between 10 and 35 bp sequences and further band extension cannot take place.
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