You lead a research team challenged with the task of creating a regulatory protein able to shut off transcription of a particular gene. You focus your design around a binding site called an operator that is associated with the promotor. The physical location of the operator most likely to affect transcription would be

Question

A.  upstream of the gene promoter.
B.  downstream of the gene promoter.
C.  internal to the gene itself.
D.  internal to the gene promoter.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

Gather Content
· What do you already know about operators and repressors?

Consider Possibilities
· What other information is related to the question? Which information is most useful?
 Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

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?

Answer 1

B.  downstream of the gene promoter.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses the function of operators an repressors.
· 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 An operator is a site on the DNA that can attract a repressor protein to block transcription.

Gather Content
· What do you already know about operators and repressors?
        o Repressors are proteins that bind to regulatory sites on DNA called operators to prevent or decrease the initiation of transcription. They act as a kind of roadblock to prevent the polymerase from initiating effectively.

Consider Possibilities
· What other information is related to the question? Which information is most useful?
        o When we learned about the lac repressor, we learned that it binds the operator site just downstream of the promoter. When the repressor protein is bound, it blocks RNA polymerase and prevents transcription.
        o Likewise, when we learned about the trp repressor, we learned that it binds the operator site just downstream of the promoter. When the repressor protein is bound, it blocks RNA polymerase and prevents transcription.
 Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Operator sites are location just downstream of the promoter, because when the repressor protein binds, it acts like a roadblock to prevent transcription by RNA polymerase.

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 where an operator site is typically located to block transcription.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that operator sites lie downstream of the promoter, so that when the repressor binds it acts like a roadblock?