Production of the iron-storing protein ferritin is regulated by aconitase, which binds to a 30-nucleotide sequence at the beginning of the ferritin mRNA and interferes with ribosome binding. Aconitase must be a

Question

A.  transcription repressor protein.
B.  translation repressor protein.
C.  RNA interference protein.
D.  translation initiation protein.

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 translational regulation?

Consider Possibilities
· Consider the different answer options. Which can you rule out?

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.  translation repressor protein.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses translational regulation.
· 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 Ferritin is the gene whose expression is regulated in this question.
        o Aconitase is the regulator protein.
        o The ribosome is the complex which carries out translation.

Gather Content
· What do you already know about translational regulation?
        o Translational regulation controls gene expression by regulating the amount of protein produced.

Consider Possibilities
· Consider the different answer options. Which can you rule out?
        o Since aconitase binds the mRNA to block ribosome binding, does that make it a transcription repressor protein? No, because the ribosome is involved in translation.
        o Since aconitase binds the mRNA to block ribosome binding, does that make it an RNA interference protein? No, RNAi works by small RNA binding the mRNA sequence, leading to cleavage of the mRNA.
        o Since aconitase binds the mRNA to block ribosome binding, does that make it a translation initiation protein? No, because in this case it is blocking translation.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Since aconitase binds the mRNA to block ribosome binding, does that make it a translation repressor protein? Yes!
 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 you to describe the role of aconitase in the regulation of ferritin.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that since aconitase blocks ribosome binding to the mRNA, it must be a repressor of translation?