Term
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Definition
| Any substance active in pattern formation whose spatial concentration varies and to which cells respond differently at threshold concentrations. |
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Term
| How does bicoid gather? How do we know it's a morphagen? |
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Definition
It's mRNA and proteins gather in the anterior end of the egg.
To find out if bicoid is a morphagen we stain it with an antibody, then we follow it's activity and concentration as different segments form. |
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Term
| How does cleavage occur in the early drosophila embryo? |
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Definition
| After fertilization there is rapid nuclear division but no cell walls form, the result being a syncytium of many nuclei in a common cytoplasm. After the ninth round of karyokinesis the nuclei move to the periphery to form the syntical blastoderm. After about 3 hours the cell walls develop, giving rise to the cellular blastoderm. About 15 pole cells will give rise to germ cells and form a separate group at the posterior end of the embryo. |
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Term
| Explain the French Flag model. |
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Definition
Cells differentiate with contrasting fates depending on the concentration of the morphagen.
As the concentration reaches a threshold cells differentiate accourding to that concentration threshold this is quantitative, from a qualitative signal.
Any substance that can direct the development of cells in this way are morphogens. |
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