Decisions about axis formation are made very early in development, when the primitive streak (see week 2 notes) first forms on the nearly symetrical embryo disc, and continue through embryogenesis. How these decisions are made, sets a key developmental question abour pattern formation.
New 2011 Molecular Development
All embryos occupy 3 D space and appear differently externally and internally within this space. This gives us 3 different body axes which need to be determined: Head/Tail (rostro/caudal), Front/Back (anterior/posterior), and Left/Right. There is the additional 3 axes needing to be determined or individual structures, but of main interest are the Limbs.
The left/right axis appears at first mirror symetrical, and looks very similar externally, but clearly many internal organs are not duplicated (heart, liver, brain etc). Each particular axis of the embryo appears to be independently established using a number of different developmental mechanisms decribed on the following pages: Early, rostro/caudal ,anterior/posterior , Left/Right , Limb
The first page of Developmental and System Notes usually contains some information about mechanisms of development that include molecular mechanisms. In order to keep the introductory page simple, detailed molecular mechanisms have been placed on a separate page (Page 11) of each section of notes. Below is a list of direct links to specific Molecular Development Pages.
| Molecular System Notes |
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| Axis Formation | Early | Limbs |
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Signaling during development, though complex, can also be grouped into a few specific classes. These mechanisms have also been listed and described briefly on Signaling Mechanisms page.
Lecture Notes |
Please note that these notes only relate to an earlier Course and not all Lecture notes and research material have been transferred. |
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Simple pictures illustrating the early events of fertilization. |
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Figures and text relating to early events of spinal cord formation. |
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Text relating to the molecular events of sex determination in the embryo. |
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A short comparison of establishing positional information in embryos. |
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The fly mutation that opened the field of Hox Genes and the conservation of pattern formation control mechanisms between species in embryonic development. |
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This section of notes introduces the topic of axes formation which establishes body patterns in multicellular organisms.
While the final animals are significantly different, the mechanisms that regulate axis formation have common molecular pathways and signals.
An excellent example is the patterning of the limb, which has been a model for axis formation.
Molecular mechanisms of development is an exciting area and requires a variety of different skills. This page introduces only a few examples and should give you a feel for the topic.
Please email Dr Mark Hill if you wish to make a comment about this current project.