Please answer ALL PARTS of questions 1-3. Thank you! Transcription. 1. Below is
ID: 64451 • Letter: P
Question
Please answer ALL PARTS of questions 1-3. Thank you! Transcription. 1. Below is one way that the orientation of genes can be drawn (from NCBI gene). Name one gene that uses the top strand as template and one gene that use the bottoms strand as template. a. Top strand as template? b. Bottom strand as template? 2. Explain how the bacterial RNA polymerase knows which strand to use as template and which direction to move? 3. Define basal levels of transcription. What factor(s) determine basal levels of transcription In bacteria? In eukaryotes?Explanation / Answer
1. a. The gene which uses top strand as template is tbx-2
b. The gene which uses bottom strand as template is sex-2
2. In most prokaryotes, a single RNA polymerase species transcribes all types of RNA. The beta () subunit has a molecular weight of 150,000, beta prime () 160,000, alpha () 40,000, and sigma () 70,000. The subunit can dissociate from the rest of the complex, leaving the core enzyme. The complete enzyme with is termed the RNA polymerase holoenzyme and is necessary for correct initiation of transcription, whereas the core enzyme can continue transcription after initiation. The core enzyme contains two polypeptides, one polypeptide, and one polypeptide. The addition of the subunit allows initiation at promoter sites.
The regions of the DNA that signal initiation of transcription in prokaryotes are termed promoters. These regions have been termed the 35 and 10 regions because of their locations relative to the transcription initiation point. Physical experiments have confirmed that RNA polymerase makes contact with these two regions when binding to the DNA. The enzyme then unwinds DNA and begins the synthesis of an RNA molecule. The dissociative subunit of RNA polymerase, the factor, allows RNA polymerase to recognize and bind specifically to promoter regions.
3. Basal level means a low level of transcription, that is driven by the pre-initiation complex alone.
At many promoters, in the absence of regulatory proteins, RNA polymerase binds only weakly. When polymerase does occasionally bind, however, it spontaneously undergoes a transition to the open complex and initiates transcription. This gives a low level of constitutive expression called the basal level. Binding of RNA polymerase is the rate limiting step in this case. Only binding of RNA polymerase determines the rate of basal transcription.
Basal or general transcription factors are necessary for RNA polymerase to function at a site of transcription in eukaryotes. They are considered the most basic set of proteins needed to activate gene transcription, and they include a number of proteins, such as TFIIA (transcription factor II A) and TFIIB (transcription factor II B), among others.
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