Parts a, b, and c 5. Recall the ZPA and AER, and their roles in limb growth and
ID: 272983 • Letter: P
Question
Parts a, b, and c
5. Recall the ZPA and AER, and their roles in limb growth and patterning. Anterior Limb bud AER ZPA Limb buds Posterior Embryos with their AER removed show no limb outgrowth, and weak A-P digit patterning. Given these results, embryos, compared to embryos with intact AERs, and explain your answer. a. describe the concentration gradient and amount of SHH that you expect to find in these Predict the limb morphology of embryos that have half of their AER transplanted to ectoderm on the ventral side, and explain your answer. b. You isolate a protein secreted by cells of the AER called Fibroblast Growth Factor (F that it is the inductive signal that causes normal this hypothesis and explain the results that would confirm your prediction (note: FGF has developmental sequences and so you cannot knock out the gene or eliminate its transcript GF), and hypothesize limb outgrowth. Describe an experiment that would test C. a role many ion). (4)Explanation / Answer
a. AER removed but ZPA intact interaction between these two is important because ZPA produces SHH, as there is no AER , SHH cannot act on AER, but its concentration gradient is intact compared to normal embriyos.
b. if half of the AERs transplanted to ectoderm on their ventral side develop in to limbs without digits because there is no ZPA and SHH protein to make digits on the limbs. other remaining intact half on dorsal side devlops in to normal limb with all digits.
c. Usually AER produces EGF 2,4,8,9,10 which play a role in limb development. we can do a experiment in which Remove the AER and externally inject EGF 2,4,8,9,10 in the removed AER area and you can see the normal limb growth, this is because studies have showed that some of EGFs act as AER for the development of limbs, ofcourse if we provide externally no need to have AER region for the normal development of the limb.