[Campbell Biology P.1111] Which of the following statements accurately describes the roles of... | Practice Question

Which of the following statements accurately describes the roles of the Apical Ectodermal Ridge AER and the Zone of Polarizing Activity ZPA in vertebrate limb development, according to the text?

  • A: The AER is a mesodermal tissue that regulates the anterior-posterior axis.
  • B: The AER is a thickened area of ectoderm that secretes FGF to promote limb-bud outgrowth along the proximal-distal axis, while the ZPA is a specialized block of mesodermal tissue that regulates development along the anterior-posterior axis.
  • C: Both the AER and ZPA primarily influence the dorsal-ventral axis of the limb.
  • D: Surgical removal of the ZPA blocks limb outgrowth along the proximal-distal axis.

Explanation

The text states that the AER is a "thickened area of ectoderm at the tip of the bud" and that "Surgically removing the AER blocks outgrowth of the limb along the proximal-distal axis." It also mentions that AER secretes FGF to promote this outgrowth. For the ZPA, it's described as a "specialized block of mesodermal tissue" that "regulates development along the anterior-posterior axis of the limb." This directly supports option B.