Which animal is likely to have the lowest expression level of a Pax6-like gene?

Question

A.  A surface-dwelling population of Astyanax mexicanus fish
B.  A cave-dwelling population of Astyanax mexicanus fish
C.  A fruit fly, Drosophila melanogaster
D.  A ribbonworm (Lineus sanguineus) developing normally
E.  A ribbonworm (Lineus sanguineus) with a regenerating head

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 gene Pax6?
 
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.  A cave-dwelling population of Astyanax mexicanus fish

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses the gene Pax6.
· 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 Pax6 is an ancient gene used in the development of eyes throughout the animal kingdom.
 
Gather Content
· What do you already know about the gene Pax6?
 
Consider Possibilities
· Consider the different answer options. Which can you rule out?
        o Would Pax6 expression be low or absent in a fruit fly, Drosophila melanogaster? No. Drosophila use a Pax6-like gene in the development of their eyes.
        o Would Pax6 expression be low or absent in a ribbonworm (Lineus sanguineus) developing normally? No. Lineus use a Pax6-like gene in the development of their eyes.
        o Would Pax6 expression be low or absent in a ribbonworm (Lineus sanguineus) with a regenerating head? No. Even during regeneration, Lineus use a Pax6-like gene in the development of their eyes.
        o Would Pax6 expression be low or absent in a surface-dwelling population of Astyanax mexicanus fish? No. It would be high because it supports eye development in the normal  (non-cave-dwelling) fish.
 
Choose Answer · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Would Pax6 expression be low or absent in a cave-dwelling population of Astyanax mexicanus fish? Yes. Cave populations of Astyanax are eyeless, because Pax6 expression is reduced.
 
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 animal will have the lowest level of Pax6 expression?
        o The question required you to take what you already know and apply it to this unfamiliar situation.
         o Did you recognize that both invertebrates and vertebrates use Pax6 in eye development?
        o Did you remember that cavefish eyes degenerate because of a reduction in the expression of Pax6?