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Developmental Biology Final
Terms in this set (57)
Maternal factors are
mRNAs and proteins packaged into the egg by the mother, which act to control early development in the embryo
The role of maternal factors (such as Vg-1, Xwnt-1, and VegT) packaged into the vegetal region of the Xenopus oocyte is
in establishing the future dorso-ventral body axis.
Between fertilization and the first cleavage division, actin filaments pull the cytoplasm of the frog egg toward the point of sperm entry in a process called
In frogs, maternally packaged Xwnt-11 leads to nuclear localization of _____ in the _____, which in response signals to adjacent cells to become the _____
â-catenin, Nieuwkoop center, Spemann organizer
What is the difference between "fate" and "specification"?
The fate of a cell is determined by labelling that cell and following it during normal development, whereas the specification state of a cell is determined by culturing a cell in an artificial medium and observing what tissues form from it.
A fate map of a Xenopus blastula, just before gastrulation begins, shows (Figure 4.9) that the top portion of the embryo will become ectoderm (skin and nerve), the central portion will become mesoderm (bone, muscle, and blood), and the lowest portion will become endoderm (gut). How is it that the endoderm and mesoderm, shown on the outside in the fate map, end up on the inside in the embryo after gastrulation?
The endodermal cells begin first to move into the embryo through the blastopore, displacing the blastocoel and forming a gut; as gastrulation proceeds, the blastopore spreads sideways and the mesoderm follows the endoderm in, ending up between the endoderm and the ectoderm.
If cells from the animal pole of a frog blastula (animal cap cells) are placed into contact with cells from the vegetal hemisphere, after removing the cells fated to form mesoderm, what is the result?
Animal cap cells are induced to form mesodermal derivatives.
The "mid-blastula transition" is the point in development when
transcription of zygotic genes begins.
What is the mechanism by which cells fated to be mesoderm form in the marginal zone of the Xenopus embryo?
Secreted signals of the TGF- family are released by the cells of the vegetal region and act on the adjacent cells of the marginal zone to instruct them to adopt a mesodermal fate.
How is the Spemann organizer distinguished from the other mesodermal cells during induction by the cells of the vegetal region?
-catenin, which has become localized to the nucleus in the Nieuwkoop center as a result of cortical rotation, turns on high levels of the TGF- signalling molecule, Nodal, and this relatively high level distinguishes the adjacent cells of the Spemann organizer from the rest of the mesoderm.
Patterning of the Xenopus mesoderm along the dorso-ventral axis involves an antagonistic relationship between chordin and BMP-4. Is there an analogy here to dorso-ventral patterning in the Drosophila embryo?
Yes, the Drosophila homolog of BMP-4, Decapentaplegic (Dpp), is antagonized by the Drosophila homolog of chordin, short gastrulation (Sog), in patterning of the dorso-ventral axis.
The grafting of the dorsal lip of the blastopore from an early Xenopus gastrula onto the ventral side of an early embryo will result in
the formation of two sets of anterior structures joined along the ventral axis: a two-headed embryo
The "default model" for neural tissue formation states that
Neurectoderm formation is inhibited by the BMP proteins present throughout the early embryo, and this inhibition is relieved by BMP antagonists from the organizer, such as chordin
In what genetic background could beta-cateninturn on target gene expression without Wnt protein?
Gain of function mutation of Frizzled protein
Mutation of APC that fails to form complex with Axin
Null mutation of GSK-3beta
Which of the following statements regarding TGF-beta signaling is FALSE?
Type II receptor determines what types of Smad proteins are activated in the pathway
Type I and Type II receptors form dimers upon ligand binding
Type I receptor is phosphorylated by Type II receptor
Activation of Smad proteins 4,5 and 8 induces ventralization of mesoderm
Activin and Nodal induce dorsal mesoderm
The central nervous system is derived from _____, the axial skeleton is derived from _____, and the muscles of the trunk are derived from _____?
ectoderm, mesoderm, mesoderm
What would be the effect on the timing of somite formation, if a piece of the pre-somitic mesoderm of a chick embryo is rotated by 180° and reinserted in its original position?
the timing of somite formation will be reversed in the rotated block only, proceeding from posterior to anterior, but the rest of the somites will form in a normal fashion, proceeding from anterior to posterior
Relative to the primitive streak and Henson's node, somite formation in the chick embryo occurs
Anterior to Henson's node, after the primitive steak has retracted past that point.
What observation might explain how somites originally become specified to form structures appropriate to their position along the antero-posterior axis?
Periodic waves of c-hairy1 are expressed in the presomitic mesoderm, such that cells in the more anterior somites will have been exposed to fewer waves of c-hairy1 than the cells in more posterior somites.
What may be the molecular trigger that causes cells in the presomitic mesoderm to finally condense into somites?
The FGF gradient drops off in the region that is forming somites.
encode transcription factors which specify a position along the anterior-posterior axis in vertebrates
The effect of grafting an extra piece of notochord into a dorsal position adjacent to pre-somitic mesoderm is
signals from the notochord will convert presumptive dermomyotome into sclerotome
Remarkably, Vg-1 and wnt are used in both frogs and chicks to establish a body axis, although in chicks this is the antero-posterior axis instead of the dorso-ventral axis. What is the region of the chick embryo that is thus analogous to the Nieuwkoop center?
posterior marginal zone
Although the vertebrate body plan outwardly displays a mirror-image symmetry with regard to left and right, the internal organs are not symmetrical. How does this left-right asymmetry develop?
Differential release of Ca2+ ions on the left side leads to expression of Nodal and Pitx2 on the left.
Which of the following is NOT involved in left-right asymmetry of vertebrates?
Epidermal growth factor
At the blastocyst stage during mammalian embryonic development, the specification of trophectoderm requires ________; whereas in inner cell mass _________activation is essential.
neural plate border
border between neuroectoderm and non-neural ectoderm (prospective epidermis)
site of neural crest induction
Notch signaling from neural plate activates hairy gene which activates signals from Wnt and Fgf and intermediate levels of BMP
CNS is derived from
PNS (sense organs and sensory nerves/ganglia) is derived from
neural crest and placodes in cranial region
only neural crest in trunk
Neural crest cells are
transient embryonic cells
Neural crest cells undergo what type of transition from neural folds to destination
Neural furrow, neural groove, neural folds, neural tube
BMP levels are inhibited in _____ and high in the _____
neural plate; epidermis
Prior to migration from neural folds, neural crest cells are
specified as premigratory neural crest cells through gene expression of FoxD3 Pax3/7
Nc expression of Phox 2b differentiation gene gives rise to
neurons and glia
Nc expression of Sox9 differentiation gene gives rise to
cartilage and bone
Nc expression of Mitf differentiation TF gives rise to
NC cells undergo EMT from neural tube and migrate along
sterotypical streams along A-P axis
in ovo electroporation is an experimental technique used to
deliver DNA into embryo or cells by using an electrical pulse to open pores in cell membranes
experimental technique to prove that a cell is multipotent
single cell lineage tracing
(the goal is to show that a single cell is able togive rise to daughter cells that can differentiate into different cells)
NC derivatives are not essential for survival so therefore problems in neural crest development causes
most congenital birth defects (craniofacial)
such as cleft lip, treachers collin syndrome, piebaldism
Transcription factors such as MITF, sox9, phox2b act
Gene regulatory network (GRN) shows
relationships between time (top-down) and space (different cell types) that control gene transcriptions
can be used to precisely define a series of molecular actions needed to recreate a developmental outcome in a progenitor or stem cell in culture for regeneration purposes or
as a roadmap for resolving developmental errors in genetic therapy
ectodermal thickenings of the embryonic head that form neurons and sense organs
transient embryonic cells
placode derivatives from pan-placodal primordium around neural crest and neural border include
cranial sensory ganglia:
- trigeminal nerve (V)
-cochlear-vestibular nerve (VIII)
placode ingresses from
ectoderm to mesoderm to form sensory ganglia through cell-cell interactions with neural crest cells
placode cell movements
invagination, ingression, delamination
paraxial mesoderm on either side of notochord and neural tube that form in anterior to posterior fashion
sclerotome (vertebrae and rib cartilage)
dermatome (dermis of back)
myotome (muscles of back, ribs, and limbs)
connection between neural crest and somites
neural crest migrates through anterior half of somites resulting in segmented pattern of peripheral sensory nerves
Ephrin and Eph cell repulsions underly neural crest migration
In the trunk, NC cells in the dorsolateral pathway form the
In the trunk, NC cells in the ventral pathway form the
neurons and glia of sensory ganglia
4 major processes in somitogenesis
1) periodicity- timing of segmentation
2)epithelialization- PSM that comes together to form a somite must undergo mesenchymal-to-epithelial transition
3)specification- of PSM by somite boundary and A-P patterning
4)differentiation- different somites along A-P boundary form different structures
induced pluripotent stem cells do not require an egg. Instead pluripotency genes such as_____ are added to adult human fibroblasts in culture via transfection
sox2, Nanog, Oct4, Klf4, c-Myc,
induced Pluripotent stem cells are characteristic of
Embryonic Stem cells
can be created from the tissue of the same patient that will receive the transplantation, thus avoiding immune rejection
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