docs.google.com OCX ielp CL: Morphogenesis Recall that the ZPA is a block of mes

Question

docs.google.com OCX ielp CL: Morphogenesis Recall that the ZPA is a block of mesodermal tissue responsible for inducing (there's that word againl) development of the anterior-posterior (AP) axis of the limb, with cells nearest the ZPA forming the most posterior digit (pinky). Anbt the ZPA, is a peripheral block of ectoderm called the Apical Ectodermal Ridge (AER). ther structure that influences limb development, and forms before Anterior A Limb bud! -AER ZPA Limb buds Posterior Early in morphogenesis you remove the AER from a set of mouse embryos, and two things happen: The limb buds stop growing outward, AND limbs produce stubby digits without A-P patterning. Based on this data, describe one probable function of the AER. Hypothesize how it might also influence formation of the ZPA. 1. MacBoolk 4 5 6 8 9 0

Explanation / Answer

AER Maintain the limb mesenchyme in a mitotically active state and focused on its task – the distal outgrowth of the limb Apical ectodermal ridge sustain expression of the molecules that establish the anterior-posterior axis. The FGFs secreted by the AER act upon the mesenchyme cells – including the zone of polarizing activity (ZPA). Thus, the AER causes the ZPA to continue secreting Sonic hedgehog (Shh), which is involved with Hox geneexpression in establishing the anterior-posteriorpolarity in the developing limb.

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