Use the following to answer questions :
Refer to the figure below showing a stage in limb development in a human embryo.
-The substance secreted by the ZPA is _______ and the concentration of this is lowest at the region labeled _______.
A) the protein Sonic hedgehog;2
B) the Shh gene;2
C) the transcription factor that turns on the Shh gene;1
D) the ZPA1 protein;2
E) the protein product of the zone of polarizing activity;1

Question

Use the following to answer questions :
Refer to the figure below showing a stage in limb development in a human embryo. 
-The substance secreted by the ZPA is _______ and the concentration of this is lowest at the region labeled _______.
A) the protein Sonic hedgehog;2 
B) the Shh gene;2 
C) the transcription factor that turns on the Shh gene;1 
D) the ZPA1 protein;2 
E) the protein product of the zone of polarizing activity;1

Quizplus · Accepted Answer

The substance secreted by the ZPA is the protein Sonic hedgehog, as stated in option A. The concentration of Sonic hedgehog is lowest at the region labeled 2, which is the anterior of the limb bud.

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