Summary
Signalling molecules whose concentration gradient instructs cells to adopt different fates.
In depth
Bicoid in the fly embryo forms an anterior-to-posterior gradient, and cells read thresholds. Sonic hedgehog patterns the neural tube ventral-to-dorsal. The French flag model by Lewis Wolpert explains positional information.
Cells interpret morphogen levels with threshold responses. Gradients form by diffusion, transport and degradation. Scaling ensures patterns fit embryo size.
Example: Turing's reaction-diffusion model explains spots and stripes.
A morphogen is a signalling molecule that forms a concentration gradient across a tissue and gives cells positional information: different thresholds switch on different genes. This is the idea behind Lewis Wolpert's French flag model.
Examples include Bicoid in the fly embryo, Sonic hedgehog in the neural tube and limb, BMP/Dpp, Wnt and retinoic acid. Gradients form by diffusion, transport and degradation, and cells read them with precision despite noise.
Example: high Shh near the notochord induces floor plate cells, while lower levels give motor neurons and interneurons.
Remember: a morphogen acts directly at a distance in a dose-dependent manner, unlike a simple on-off signal.
Frequently asked questions
What is Morphogens?
Signalling molecules whose concentration gradient instructs cells to adopt different fates.
Which area of biology covers Morphogens, and how advanced is it?
Morphogens 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 Induction, Hedgehog Signalling, BMP and TGF-Beta Signalling.
Can you give an example of Morphogens?
Retinoic acid helps pattern the hindbrain.
What should I learn before Morphogens?
Work through the Beginner topics in Developmental Biology first, such as Fertilisation, Zygote, Embryo, then return to Morphogens. Intermediate topics assume the Beginner vocabulary.
What topics are related to Morphogens?
The closest topics to Morphogens are Induction, Hedgehog Signalling, BMP and TGF-Beta Signalling, Limb Development. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Morphogens?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Morphogens. To practise the whole of Developmental Biology, use the Developmental Biology quiz.
How is Morphogens different from Induction?
Morphogens: Signalling molecules whose concentration gradient instructs cells to adopt different fates. Induction: One group of cells signals a neighbouring group to change its developmental path. Read both side by side and note what each one explains.
How should I study Morphogens 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 Induction and explain the difference aloud. Finally, take the Developmental Biology quiz and come back to this page for any question you miss.