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CMMB 403 Final UPDATED Actual Exam Questions and CORRECT Answers

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CMMB 403

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CMMB 403

CMMB 403 Final UPDATED Actual Exam Questions and CORRECT Answers What are the origins of the optic vesicle and the lens? - CORRECT ANSWER- optic vesicle = forebrain (neural ectoderm) lens = surface epidermis --> placode Describe the process of lens induction - CORRECT ANSWER- 1. the opti...

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CMMB 403 Final UPDATED Actual Exam
Questions and CORRECT Answers
What are the origins of the optic vesicle and the lens? - CORRECT ANSWER✔✔- optic
vesicle = forebrain (neural ectoderm)
lens = surface epidermis --> placode

Describe the process of lens induction - CORRECT ANSWER✔✔- 1. the optic vesicle
(forebrain) induces thickening of the surface epidermis (prospective lens placode)
2. the optic vesicle pinches in to form the optic cup and the lens invaginate as well (lens
placode comes into contact w/ the optic vesicle)
3. the optic cup forms two layers: neural retina and the pigmented retina
4. the lens pinches off

What is a placode? - CORRECT ANSWER✔✔- epithelial thickening of ectoderm that
develops into neurons or other parts of the sensory organs

What is the function of jervine? - CORRECT ANSWER✔✔- Its a SHH inhibitor, preventing
the repression of Pax6 at the midline, causing cyclopia

What is the function of Pax6? - CORRECT ANSWER✔✔- Eye development

Where is Shh expressed along the midline? - CORRECT ANSWER✔✔- - the prechordal
plate (floor plate of the neural tube) and the notochord

How does the signalling in Mexican cave-dwelling fish differ for eye development? -
CORRECT ANSWER✔✔- - they sent need to see because they live in caves
- so they have evolved to over express Shh and down regulated Pax6 everywhere = no eye
development

What is the function of the Rx gene? - CORRECT ANSWER✔✔- retinal development -->
functions to maintain the expression of Pax6 (AMPLIFY PAX6)

,Where do neural crest cells form? - CORRECT ANSWER✔✔- The entire length of the
neural tube

How do neural crest cells migrate? When in development does migration occur? - CORRECT
ANSWER✔✔- They undergo an EMT
- migrate in the 4th week of development

What transcription factors are necessary to cause the release of E-cadherin and allow the
neural crest cells to undergo an EMT and migrate - CORRECT ANSWER✔✔- Snail/Slug -->
neural crest cells lose E-cadherin and become mesenchymal and can migrate through the
body

What are the four main regions of neural crest and what do they form? - CORRECT
ANSWER✔✔- 1. Vagal/ Sacral: forms the parasympathetic neurons that innervate the gut
2. trunk: forms the sensory neurons and dorsal root ganglia (and the melanocytes)
3. cranial: forms the bones and cartilage of the face
4. cardiac: forms the outflow tracts of the heart

What chemotaxis elements are responsible for the migration of the vagal/sacral neural crest
cells into the gut? - CORRECT ANSWER✔✔- gut produces GDNF signal which binds to the
RET receptors on the neural crest cells --> chemoattraction that drives the movement of
neural crest cells into the gut

What causes Hirschprungs disease? - CORRECT ANSWER✔✔- mutation in GDNF or the
RET receptor to prevent chemoattraction driving the movement of neural crest cells to the gut
- dont get proper peristalsis in the gut anymore

What are the two pathways that trunk neural crest cells can migrate down? Which one forms
what and which happens first? - CORRECT ANSWER✔✔- First - the ventral pathway:
neural crest cells migrate to the anterior sclerotome where they either become the
sympathetic ganglia or the dorsal root ganglia

Second - the more dorsolateral pathway: future melanocytes migrate between the dermis and
epidermis

,Where are the cell bodies of the sensory neurons found? - CORRECT ANSWER✔✔- - found
in the dorsal root ganglia, not right in the central nervous system

What drives the migration of trunk neural crest through the anterior sclerotome instead of the
posterior? - CORRECT ANSWER✔✔- - the neural crest cells express Eph receptors
- the posterior sclerotome expresses ephrins
- these repel eachother

What do the neural crest cells who stay in the anterior sclerotome become? - CORRECT
ANSWER✔✔- if they stay in the anterior sclerotome --> become more dorsal cell types DRG

What do the neural crest cells who are repulsed and migrate out of the anterior sclerotome
become? - CORRECT ANSWER✔✔- cells that migrate out of the anterior sclerotome
migrate back more ventrally --> become the sympathetic ganglion

How does the migration of the axons of the motor neurons resemble the neural crest cells? -
CORRECT ANSWER✔✔- motor neuron axons also express Eph receptors and are driven to
migrate through the anterior sclerotome too

What is the cell signalling pathway required for the trunk neural crest cells to migrate through
the dermis/epidermis and become melanocytes? - CORRECT ANSWER✔✔- - melanocytes
express the Kit receptor tyrosine kinase
- the dermis expresses the SCF (stem cell factor) ligand which activates the Kit receptor on
the neural crest cells
- causes phosphorylation and activation of the transcription factor, MITF
- and causes melanocytes to proliferate and migrate

What mutations would be present in people who have skin pigmentation problems? -
CORRECT ANSWER✔✔- - problem would be in the migration of their melanocytes through
the body --> driven by the Ras pathways (via Kit repceptors and SCF ligand)
- could have a mutation in the Kit receptor on the neural crest cell
- or could have a mutation in the SCF ligand from the dermis

, What is the role of the MITF transcription factor? - CORRECT ANSWER✔✔- - MITF is a
transcription factor that activates melanoblast specific genes... it is produced when the Ras
pathway is active --> SCF is released from the dermis which activates the Kit receptor on the
melanocyte neural crest cells
- get melanocyte proliferation

What would you see in someone w/ a Kit mutation? - CORRECT ANSWER✔✔- lack of
pigmentation --> lack of melanocyte proliferation

Why are MITF mutations in dalmations and painted horses associated with pigmentation
problems and with deafness? - CORRECT ANSWER✔✔- - melanocytes also play a role in
migration to the inner ear to promote blood vessel formation in the cochlea

What do cranial neural crest cells that migrate through pharyngeal arches 1 and 2 become? -
CORRECT ANSWER✔✔- - become the middle ear: incus, malleus, and stapes

What do the cranial neural crest cells that migrate through pharyngeal arches 3, 4, and 6
become? - CORRECT ANSWER✔✔- - become the bones are cartilage of the throat and face

What are the bones of the middle ear derived from? (incus, malleus, and stapes) - CORRECT
ANSWER✔✔- middle ear bones are derived from cranial neural crest the migrated through
the first 2 pharyngeal arches

What population of neural crest cells can form bone? - CORRECT ANSWER✔✔- Only
cranial

Where do the cardiac neural crest cells migrate through? - CORRECT ANSWER✔✔- arches
3, 4, and 6

What do the cardiac neural crest cells differentiate into? - CORRECT ANSWER✔✔- - the
septum that separates the truncus arteriosis (single outflow tract that has mixed oxygenated
and unoxygenated blood) into the aorta and the pulmonary artery

How do we know that cardiac neural crest cells contribute to heart development? -
CORRECT ANSWER✔✔- - quail grafting into chick embryos

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