A. transcription initiation.
Clarify Question
· What is the key concept addressed by the question?
o This question addresses RNA polymerase.
· What type of thinking is required?
o This question is asking you to take what you already know and apply it to this unfamiliar situation.
· What key words does the question contain and what do they mean?
o A nonsense mutation is one that causes an early STOP codon, resulting in a protein that is shorter than normal.
o RNA polymerase is the enzyme that transcribes DNA into mRNA.
o The sigma (s) subunit of RNA polymerase is important in transcription initiation.
Gather Content
· What do you already know about RNA polymerase?
o RNA polymerase is the enzyme that does transcription – it produces RNA.
o There are three main steps to transcription: initiation, elongation, and termination.
o Initiation requires the polymerase to recognize and bind to the promoter. Promoter binding is controlled by the s subunit, which recognizes the –35 sequence in the promoter and positions the RNA polymerase at the correct start site, oriented to transcribe in the correct direction.
Consider Possibilities · Consider the different answer options. Which can you rule out?
o Is the sigma subunit of RNA polymerase likely to be important for translation? No, because RNA polymerase is used in transcription, not translation. The ribosome is the enzyme that carries out translation.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o Of the three aspects of transcription, loss of the sigma subunit is likely to disrupt initiation, because the sigma subunit is necessary to recognize and bind the promoter.
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o This question asked what would result from a missing RNA Polymerase sigma subunit. o The question required you to take what you already know and apply it to this unfamiliar situation.
o Did you recognize that RNA polymerase acts in transcription, not translation?
o Did you remember that the sigma subunit binds the promoter?
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