Summary
Signalling centres such as the apical ectodermal ridge and ZPA pattern limb growth and digits.
In depth
The apical ectodermal ridge (FGF) drives outgrowth, ZPA (Sonic hedgehog) specifies anterior-posterior digit identity, and Hox genes pattern. Thalidomide caused limb malformations (phocomelia).
Proximal-distal growth uses AER signals; the progress zone model has been revised. Digit number relates to Shh duration and concentration. Hox genes set positional identity.
Key idea: a few signalling centres pattern the entire limb.
Frequently asked questions
What is Limb Development?
Signalling centres such as the apical ectodermal ridge and ZPA pattern limb growth and digits.
Which area of biology covers Limb Development, and how advanced is it?
Limb Development is one of the 54 topics in Developmental Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Morphogens, Body Axes Formation, Hox Genes.
Can you give an example of Limb Development?
ZPA grafts yield mirror-image duplicated digits.
What should I learn before Limb Development?
Work through the Beginner topics in Developmental Biology first, such as Fertilisation, Zygote, Embryo, then return to Limb Development. Intermediate topics assume the Beginner vocabulary.
What topics are related to Limb Development?
The closest topics to Limb Development are Morphogens, Body Axes Formation, Hox Genes, BMP and TGF-Beta Signalling. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Limb Development?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Limb Development. To practise the whole of Developmental Biology, use the Developmental Biology quiz.
How is Limb Development different from Morphogens?
Limb Development: Signalling centres such as the apical ectodermal ridge and ZPA pattern limb growth and digits. Morphogens: Signalling molecules whose concentration gradient instructs cells to adopt different fates. Read both side by side and note what each one explains.
How should I study Limb Development step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Morphogens and explain the difference aloud. Finally, take the Developmental Biology quiz and come back to this page for any question you miss.