Term
| What is a developmental field? |
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Definition
| A group of cells that self-organise themselves to develop an organ without contribution from the rest of the embryo and self-regulate (share the same potential fates). |
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Term
| In Drosophila what are segments and what signalling molecules are involved? |
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Definition
Body segments and appendages.
The segment polarity genes (hh, en, wg and dpp) |
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Term
| What examples can you think of that act as fields? |
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Definition
Limb buds in Gallus development.
Imaginal disks in Drosophila development. |
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Term
| How do we know that zone of polarizing activity (ZPA) is important in limb bud formation? |
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Definition
ZPA is always found at the posterior junction of the young limb bud. When it is transplanted inot a position on the anterior segment of another limb bud the number of didgits of the resulting wing is doubled. Polatity is matintained, but the information is coming from an anterior and posterior direction.
This means that ZPA defines the anterior-posterior axis int he development of new limbs. |
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Term
| How do we know that Sonic hedgehog (Shh) protein influences the distribution of ZPA? |
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Definition
- The Shh gene was inserted adjacent to an active promoter of a chicken virus, and the recombinant virus was placed into cultured chick embryo fiboblast cells (CEF).
- The virally infected cells were pelleted and implanted into the anterior margin of a limb bud of a chick embryo.
- The resulting limbs produced mirror-image digits, showing that the secreted protein had polarizing activity.
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Term
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Definition
Starting from a differentiated state, cells reverse or change their differentiation in order to replace missing cell fates.
This is post-embryonic. |
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Term
| What are the difference between repair and regeneration? |
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Definition
Repair involves the differentiation of a cell from and undifferentiated cell.
Regeneration involves the de-differentation of a cell and then differentiation to a new cell type. |
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Term
| What is the difference in mitosis between a population of precursors (in repair) and stem cells (in embryonic development)? |
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Definition
Precursors undergo symetric mitosis whereby a mother cell produces two identical daughter cells.
Stem cells undergo asymetric mitosis whereby a mother cell produces a copy of herself and a differentiated daughter cell. |
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Term
| What is epimorphic regeneration? |
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Definition
| Adult cells de-differentiate and proliferate under the epidermis. Once they have formed a mass of cells they differentiate. |
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Term
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Definition
| Regeneration occurs by the remodelling of existing tissue and the re-establishment of boundaries and so it requires little growth. |
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Term
What type of regeneration occurs in amphibians?
Explain their eye regeneration. |
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Definition
Epimorphic regeneration.
Removal of the lens from the eye results in regeneration of a new lens from the dorsal pigmented epithelium of the iris. |
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Term
| What is distalization and intercalation? |
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Definition
Distalization is the regeneration from proximal stump to the distal end of a limb. (Regrowing a whole arm)
Intercalation is the regeneration of structures between a proximal host and a distal implant. (Transplanting a hand onto a stump off the shoulder and growing an arm inbetween) |
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Term
| How does intercalation happen in cockroaches-irrespective of the proximo-distal axis? |
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Definition
| When a distally amputated tibia is grafted onto a proximally amputated host intercalation of the positional values 2-4 occurs, irrespective of the proximo-distal orientation of the grafts. |
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Term
| What animals can undergo whole body regeneration? |
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Definition
| The planarian (based on stem cells), the Hydra and the Starfish. |
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Term
| Explain what happens when cells in region 1 are labelled in the Hydra. |
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Definition
The dye will be displaced to the tentacles, the basal disk and the bud.
This is due to the fact that the cells are continually dividing and being displaced. |
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