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EEB 184- Exam #2 Latest Update
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EEB 184- Exam #2 LatestUpdate
Proximal-Distal
Anterior-Posterior
Dorsal-Ventral - Answer (pic)
3 Segments of Adult Limb - Answer -Stylopod
-Zeugopod (forearm)
-Autopod (hand/foot)
Hox Genes in Limb Development - Answer -Used in patterning body axis (influences
where)
-forelimb development & hindlimb development
-controls limb PLACEMENT along body axis
How would you expect forelimb outgrowth to be impacted by shift in Hox genes
(Mutant)?
(W.T. - aligned & shifted Hox gene expression (FLANK))
(Mutant - aligned & parallel Hox gene expression (FLANK)) - Answer -Little/no limb
outgrowth
-FLANKS repressing eachother
-becomes snake (python)
Limb Induction - Answer combination of Hox genes working to make a limb
Limb Outgrowth: Cells - Answer Fgf10 (fibroblast growth factor
SHH (sonic hedgehog)
Fgf4 + Fgf8
Fgf8: becomes AER
Limb Development: Zones - Answer (pic)
,AER - Answer -drives cell proliferation & regulates limb outgrowth
-essential to limb growth
What would you expect to happen if AER was removed before outgrowth began? -
Answer -Autopod & Zeugopod would NOT form but stylopod
-Stylopod still forms since hard to remove ERD in time (see it = too late)
AER & ZPA - Answer -interact to regulate limb outgrowth & patterning
-ZPA secrets SHH protein
Assume you had 2nd ZPA to anterior side of limb. What phenotype would you expect in
resulting chick limb? - Answer Limb structures would be repeated in mirror-like pattern
In mouse #1, Shh knocked out during limb development. What would happen if a
mutation was instead introduced into the protein-coding region of Shh? - Answer
-Embryo would display deformations EVERYWHERE in many organ systems, including
limb
-since mutation in all cells - not just in limb development!
Earlier Shh was removed = _?_ digits formed - Answer fewer
Limb Development: Shh - Answer -keeps limb growing out
-big role in proliferation & determining # of digits & patterning
Shh & Cell Death Correlation - Answer -Shh not present = cell death inc.
-Shh present = cell death dec.
Interdigital tissue regression - Answer BMP: cell death to rid of webbed fingers
4 Mechanisms of Evo-Devo - Answer Heterotopy
Heterochrony
Heterotypy
Heterometry
Heterotopy - Answer change in location
-ex) duck/bat/dolphin/whales flippers
-duck: gremlin repress BMP
-bat/dolphin/whale: gremlin&FGFs represses BMP
-change in location: gremlin/FGFs
, -ducks = only gremlin!
Heterochrony - Answer change in time
-ex)whale limb development, FGF (in AER) normally shuts off, but staying on = longer
philanges (change in timing)
Heterotypy - Answer change in identity
-ex)pigeon's feathered feet:
-from no feathers -> feathers: Pitx1 dec.
-from no feathers -> feathers: Tbx5 inc.
-results in shift in identity; telling hindlimb that it's a forelimb (feathers form)
Heterometry - Answer change in amount
-ex)whale pelvis: ZPA not turned on = no Shh = nothing forms = whales w/no legs
-ex)snakes: ZPA on but AER not on properly = no limb!
Loss of whale hind limbs is the result of: - Answer Heterometry
-ZPA not turned on
The webbing of whale forelimbs is the result of: - Answer Heterotopy
-gremlin/FGFs
Hyperphalangy of whale forelimbs is the result of: - Answer Heterochrony
-FGF in AER stays on longer
Loss of digits in cows & jerboas represents: - Answer Heterotopy
-Change in place of BMPs (time as well)
Polydactyly - Answer -extra fingers/toes
-usually from Shh/ZPA/AER
-ZRS mutation (which is an Shh enhancer) = more Shh activity = more digits
Polydactyly in cats - Answer "Hemingway cats"
-mutation of dominate gene
-not uncommon
-paws look like mittens
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