You are attempting to synthesize rRNA in a test tube using DNA isolated from mouse cells. In addition to the template DNA, ribonucleotides, and the necessary transcription factors, you should also add _________ to the test tube.

Question

A.  poly-A polymerase
B.  RNA polymerase III
C.  RNA polymerase II
D.  RNA polymerase I

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 RNA polymerases?

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

D.  RNA polymerase I

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses RNA polymerases.
· 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 Ribosomal RNA, or rRNA, is the RNA component of the ribosome.
        o Template DNA is the DNA that is used to transcribe an RNA.
        o Ribonucleotides are the building blocks of RNA.
        o Transcription factors are proteins that help carry out and regulate transcription.

Gather Content
· What do you already know about RNA polymerases?
        o RNA polymerases are the enzymes that carry out transcription.
        o There are three kinds: RNA Polymerase I, II, and III, each with specialized functions.
        o RNA Polymerase I transcribes rRNA.
        o RNA Polymerase II transcribes mRNA and snRNAs.
        o RNA Polymerase I transcribes tRNA and some other small RNAs.

Consider Possibilities
· Consider the different answer options. Which can you rule out?
        o Would it make sense to add poly-A polymerase? No, only mRNAs are polyadenylated. Ribosomal RNAs are not.

Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o To decide which RNA polymerase should be added, you must remember that they each have specialized target genes, and that RNA Polymerase I is the enzyme that transcribes rRNA.

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 which enzyme was necessary to carry out transcription of rRNA.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you remember that RNA Polymerase I is specialized to transcribe rRNA?