Location of a Cell May Be Critical in the Determination

Multiple Choice

Location of a cell may be critical in the determination of its ultimate fate during development, as in the development of vertebrate limbs. This fact arises from

A) the unequal distribution of transcription factors.
B) expression of organ identity genes.
C) a gradient in the concentration of the morphogen, sonic hedgehog.
D) a gradient in the concentration of ZPA.
E) expression of homeotic genes.