[Campbell Biology P.1112] Which statement accurately describes the primary locations and deve... | Practice Question

Which statement accurately describes the primary locations and developmental roles of the Apical Ectodermal Ridge AER and the Zone of Polarizing Activity ZPA in a vertebrate limb bud, according to Figure 47.25?

  • A: AER is located on the posterior margin and specifies the proximal-distal axis, while ZPA is on the distal tip and specifies the anterior-posterior axis.
  • B: AER is located on the distal tip and specifies the proximal-distal axis, while ZPA is on the posterior margin and specifies the anterior-posterior axis.
  • C: Both AER and ZPA are located on the anterior margin and are involved in dorsal-ventral patterning.
  • D: AER is on the dorsal surface and ZPA is on the ventral surface, both regulating overall limb size.

Explanation

Figure 47.25 a and its caption clearly state that the Apical Ectodermal Ridge AER is located at the distal tip of the limb bud and is involved in pattern formation along the proximal-distal axis. The Zone of Polarizing Activity ZPA is located on the posterior margin of the limb bud and plays a key role in specifying the anterior-posterior axis. Option B correctly identifies both the locations and the primary developmental roles.