Overexpression of caudal in the early Drosophila embryo, at a level high enough to overcome inhibition by Bicoid protein, would

Question

A.  interfere with the development of anterior structures.
B.  interfere with the development of posterior structures.
C.  interfere with the development of both anterior and posterior structures.
D.  have no effect since the cytoplasm has already been determined.

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 caudal?
 
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

A.  interfere with the development of anterior structures.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses caudal.
· 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 Caudal is a gene that specifies posterior development in the Drosophila embryo.
        o Bicoid is a gene that specifies anterior development.
 
Gather Content
· What do you already know about caudal?
        o Caudal activates genes required for the development of posterior structures.
        o The caudal mRNA is evenly distributed across the egg, but the protein becomes localized, because Bicoid protein binds to and inhibits translation of caudal mRNA.
        o Therefore, caudal is only translated in the posterior regions of the egg where Bicoid is absent.
 
Consider Possibilities · Consider the different answer options. Which can you rule out?
        o Would overexpression of caudal interfere with the development of posterior structures? No, it normally specifies posterior structures.
        o Would overexpression of caudal interfere with the development of both anterior and posterior structures? No, just anterior –  it normally specifies posterior structures.
        o Would overexpression of caudal have no effect since the cytoplasm has already been determined? No, it is a powerful morphogen so it would have a disruptive effect.
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Would overexpression of caudal interfere with the development of anterior structures? Yes, since caudal specifies posterior development, it would disrupt the development of the anterior.
 
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 from overexpression of caudal.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that caudal normally specifies posterior development?