You are studying the function of a recently identified gene in C. elegans. You perform genetic screens for several months in an attempt to isolate loss-of-function gene mutations, but your efforts are unsuccessful. Your advisor suggests you try another approach to eliminate gene function. The best technique to accomplish this goal would be

Question

A.  to design a repressor to bind to the operon of this gene.
B.  use a histone deacetylase to induce a transcriptionally inactive state.
C.  use a C. elegans strain with a homozygous TFIID mutation to prevent the translation initiation complex from forming.
D.  use RNA interference to prevent mRNA translation.

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 loss-of-function mutations?

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.  use RNA interference to prevent mRNA translation.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses loss-of-function mutations.
· What type of thinking is required?
        o This question is asking you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
· What key words does the question contain and what do they mean?
        o A loss-of-function gene mutation is a mutation that “breaks” the gene, preventing it from working.

Gather Content
· What do you already know about loss-of-function mutations?
        o Loss-of-function mutations are any mutation that results in less of the normal gene activity.
        o They may be due to total deletion of the gene, or a lower level of expression of the mRNA, or because the protein cannot work at the normal rate.

Consider Possibilities
· Consider the different answer options. Which can you rule out?
        o To mimic a loss-of-function mutation in this gene, should you design a repressor to bind to the operon of this gene? Bad idea. First of all, eukaryotes like C. elegans don’t have operons. Second, even if they did that would knock out several genes at once. Third, that would be very difficult to do.
        o To mimic a loss-of-function mutation in this gene, should you use a histone deacetylase to induce a transcriptionally inactive state? No, that would probably inactivate many many genes and kill the worms.
        o To mimic a loss-of-function mutation in this gene, should you use a C. elegans strain with a homozygous TFIID mutation to prevent the translation initiation complex from forming? No, that would definitely affect all the genes and kill the worm.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o To mimic a loss-of-function mutation in this gene, should you use RNA interference to prevent mRNA translation? Yes! That is an excellent way to quickly mimic a loss-of-function mutation in one specific gene.
 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 approach would be a good substitute for finding a mutation in a gene.
        o The question required you to weigh and judge evidence, or evaluate, to choose the best of the possible answers.
        o Did you recognize that RNAi is a technique that allows a researcher to mimic a loss-of-function mutation?