You created a worm that expresses a human Bcl-2 transgene, and you are crossing the transgene into a homozygous ced-9 mutant background. However, you inadvertantly used a clone of Bcl-2 with a mutation in the BH domain, which is essential for function. What results do you expect for the ced-9 mutants with the mutant Bcl-2 transgene?

Question

A.  131 cells will die.
B.  All 1090 cells will die.
C.  All 1090 cells will live.
D.  959 cells will die.

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 the apoptosis pathway?

  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.  All 1090 cells will die.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses the apoptosis pathway.
· What type of thinking is required?
        o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.
· What key words does the question contain and what do they mean?
        o Bcl-2 is an inhibitor of the apoptosis pathway in mammals.
        o The worm gene ced-9 is homologous to Bcl-2, and also inhibits the apoptosis pathway.

  Gather Content
· What do you already know about the apoptosis pathway?
        o In worms, 131 of the 1090 cells normally die by the apoptosis pathway.
        o If the inhibitor ced-9 is mutant, then all cells die.

  Consider Possibilities · What other information is related to the question? Which information is most useful?
        o In a wild-type worm, 131 cells should die.
        o If the inhibitor ced-9 is mutant, then all cells die.
        o If that mutant carried a wild-type Bcl-2 transgene, then that would act like ced-9 and the cells would live. But...
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Since the Bcl-2 transgene is mutant in its critical BH domain, it cannot function and it may as well not be there.
        o So all 1090 cells will die.

  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 if a mutant Bcl-2 transgene was in a ced-9 background.
        o The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that normally the Bcl-2 transgene would rescue the ced-9 mutant, but with a mutation in the BH domain it can’t?