Experimental mutations in the timing of Hox gene expression cause lab mice to develop deformed limbs. This is an example of
A. evolution of a new gene to code for the new morphology.
B. homeosis.
C. heterochrony.
D. a change in spatial pattern of gene expression.
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 heterochrony?
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?
C. heterochrony.
Clarify Question
· What is the key concept addressed by the question?
o This question addresses heterchrony.
· 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 Hox genes are transcription factors that are important for controlling development along the anterior-posterior body axis in all animals.
o Deformed limbs would be legs that did not form correctly.
Gather Content
· What do you already know about heterochrony?
o Alterations in timing of developmental events due to a genetic change are called heterochrony.
Consider Possibilities
· Consider the different answer options. Which can you rule out?
o Are these mice an example of evolution of a new gene to code for the new morphology? No, there is not a new gene, just a change in the timing of gene expression.
o Are these mice an example of homeosis? No, that would be a change in the spatial pattern of gene expression. The mice are an example of a change in the timing of gene expression.
o Are these mice an example of a change in spatial pattern of gene expression? No, they are an example of a change in the timing of gene expression.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o Are these mice an example of heterochrony? Yes, because the defect is due to a change in the timing of gene expression.
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 we call it when the timing of gene expression changes.
o The question required you to take what you already know and apply it to this unfamiliar situation.
o Did you recognize that the mice with deformed limbs are an example of heterochrony?
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