Term
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Definition
| process by which cells acquire identity appropriate for their location, leads to generation of different types of neurons and glial cells |
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Term
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Definition
medial-lateral
anterior-posterior |
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Term
| neural plate stage M-L axis features |
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Definition
| roof, alar, basal, floor plates |
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Term
| neural plate stage A-P axis features |
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Definition
secondary prosncephalon-telencephalon, hypothalamus
diencephalon
mesencephalon
rhombencephalon
spinal cord |
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Term
| 1: closure of the neural tube (neurulation) |
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Definition
| M-L axis becomes D-V axis, medial becomes ventral! |
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Term
| 2: formation of 3 brain vesicles |
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Definition
| forebrain, midbrain, hindbrain |
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Term
| 3: formation of secondary vesicles |
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Definition
| optic vesicles (from forebrain) |
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Term
| 4: Increased bening along A-P axis |
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Definition
| making cephalic and cervical flexures |
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Term
| 5: A-P division of the forebrain |
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Definition
| anterior (telencephalon and hypothalamus) from posterior (diencephalon) |
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Term
| What causes regionalization? |
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Definition
- different expression of transcription factors following graded signaling of secreted proteins
- signaling centers being formed from non-neural tissue to within neural tissue to control pattern
- establishing unique progenitor cells with specific positional identity
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Term
| Why use Drosophila as prototype for A-P patterning? |
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Definition
| The form many segments: head, 3 thorax, 8-9 abdomin, and the sections can be seen in early embryos |
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Term
| where does polarization start? |
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Definition
| unfertilized oocytes with egg-polarity genes, then gap genes mark major subdivisions of the embryo |
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Term
| What type of genes are required for alternative bodysegments? |
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Definition
pair-rule genes: regulated by a combination of gap genes
[image][image] |
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Term
| How do segment polarity genes organize the embryo? |
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Definition
| they make the A-P pattern of individual segments, stabilizing the segment boundaries, these genes can help each other be expressed to further strengthen the segmentation |
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Term
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Definition
mutations that make parts of the body into something appropriate for a different section of the body (e.g. legs on the head instead of antennae)
homeotic selector genes ensure this doesn't happen |
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Term
| what do homeotic selector genes code for? |
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Definition
| DNA-binding proteins; order of the genes on the chromosome determines the order in which they are expressed on the AP axis (co-lineality) |
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Term
| What do Hox genes control in vertebrates? |
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Definition
| A-P axis (4 complexes: A, B, C, D) |
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Term
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Definition
| 180 nucleotide DNA squence encoding the homeodomain |
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Term
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Definition
| genes containing a homeobox |
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Term
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Definition
| genes located on the Hox cluster (fly)/Hox A-D clusters (vertebrate), (containing the homeobox) |
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Term
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Definition
| describes homeotic tranformation |
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Term
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Definition
| group of cells that can induce a fate in neighboring cells and pattern nearby tissues |
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Term
| Spemann organizer/Hensen's node |
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Definition
can induce nervous system cells in non-neural plate fated cells, appropriately patterned result
[image]
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Term
| Spemann organizer/dorsal lip cell fate |
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Definition
becomes axial mesoderm that underlies (and induces) what will be the neural plate
[image] |
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Term
| head-trunk-tail organizer model |
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Definition
model where there are organizers for each region of the body that induce the formation of that region
(molecules aren't exactly secreted by the organizer in a regional fashion)
[image] |
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Term
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Definition
Wnt promotes β-catenin production which leads to transcription of Axin2, cyclins, etc.
[image] |
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Term
| Activation-Transformation Model |
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Definition
induction of rostral neural character (activation) is an early step in nervous system formation, and later signals modify parts (transformation) to generate more caudal/posterior regions
1st: head. 2nd: head neural tissue.
[image] |
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Term
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Definition
| descendants of the organizer, beneath neural plate |
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Term
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Definition
| produces caudalizing factors, doesn't induce neural tissue by itself |
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Term
| activating and transforming agents |
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Definition
activation: BMP antagonists
transformation: Wnt, FGFs, retinoic acid |
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Term
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Definition
| doesn't induce neural tissue by itself, but blocks Wnt, BMP, and Node pathways to prevent caudalization |
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Term
| early regionalization signals |
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Definition
| come from outside the neural tissue, set up very broad A-P identity of the nervous sytem using mutually suppressive transcription factors Otx2 and Gbx2 (both homeobox genes) |
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Term
| 4 major steps to brain regionalization |
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Definition
- ectodermal cells acquire neural identity
- vague positional character A-P (from axial mesoderm), anterior goes away from caudalizing factors like Wnts
- local signal sources established e.g. floor plate
- these "secondary organizers" refine further regional patterning
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