Unit 2 Exam Flashcards
The fertilization envelope…
separates the contents of the nucleus from the cytoplasm and provides the structural framework of the nucleus
Cadherins function via direct binding between cadherin molecules on one cell and…
Cadherin molecule of another cell
Cells tend to form aggregate…
- Depend on the type of cadherin it possess
- To reflect their respective positions in the embryo
- To show selective affinity
The cell surface tension ….
- Dependent on the level of adherin molecule
- Determines the localized position of the cell type
- Highest in the center
Which one of the following is not a juxtacrine signaling system?
Cell communication that requires direct contact
- FGH, Hedgehog, wnt, TFG-n, Hippo
The receptor for Wnt …
Wnt binds to Glypican, a HSPG, on a nearby cell when secreted. Glypican transfers Wnt to the Frizzled receptor, causing a secretion of Notum to cleave Wnt’s lipids-signaling molecules that regulate cell-to-cell interactions during embryogenesis. Wnt proteins bind to receptors of the Frizzled and LRP families on the cell surface.
Which of the following molecules has a role in sperm chemotaxis in vertebrates?
Crisp-1 and calcium
Which of the following genes are expressed during amphibian eye induction?
- Otx2, Pax6, Sox3
- bmp4 AND fgf8
In the absence of a Wnt signal…
GSK is active and cytosolic beta-catenin is constantly degraded
The hippo pathway plays a role in the inner mass formation…
- of organ size
- controls Proliferation
- Involved in apoptosis
- stops mitosis
The acrosomal reaction (in animals with internal fertilization) can occurs at the level of ..
- Jelly layer
Heparan Sulfate proteoglycans are important for
- directing diffusion of Fgf8
- Fostering the congregation and secretion of hedgehog molecules as lipoprotein assemblies
- keeps secreted Wnt close to the secreting cellptk signal transduction pathway activated by FGF ligand
- which restricts diffusion and accumulates wnt closer to source of production
Lens formation can be induced…
- by the optic vesicle signaling or mesenchymal induction
- in the presence of necessary transcription factors
- By Pax6, a paracrine factor required for the surface ectoderm to respond to the inductive signal of the optic vesicle
Can the Acrosomal reaction happen before the contact of the zona pelucida
Yes
During Epithelial-mesenchymal transition
The mesenchymal cell, originally part of the epithelial, receives paracrine signals to release itself from the basement membrane by dissociating the apical polarity complexes and adheren junctions binding them to adjacent cells
Thanatotropic dysplasia …
FgfR3 gain of function mutation causes premature activation of STAT pathway
Block of chondrocyte proliferation
-lethal dwarfism
Which of the following molecules are part of the Hedgehog signaling pathway?
Smoothened
Patched
PKA
Slimb
Ci (drosophila)
Gli (vertebrates)
Cos2
CK1
GSK3
no Hedgehog
-Patched-> smoothened-> degredation
-ci is therefore cleaved by PKA cause Ci to be a repressor
Wnt1 non-canonical pathway (Planar Cell polarity)
- mediates asymmetric cytoskeletal
- it is important in cell migration and there is no participation of LPR5 (instead, RhoaRac)
- binds to Ror and Frizzled at cell surface
- Influences cell behavior AKA Wnt/calcium pathway b-catenin independent causes changes w/in the cytoplasm that influence cell function, shape and behavior
At the time of sperm entry, the mammalian egg is
- Diploid
- The ovum, is encased in the zona pellucida, which in turn is surrounded by the cells of the cumulus
- A polar body cell, produced during meiosis, is visible within the zona pellucida
At the time of sperm entry, the sea urchin egg
- haploid
- 3 polar bodies
Sea Urchin acrosomal reaction involves
- FSP (fucose sulfated polysaccharide) binding to receptor on sperm plasma membrane
- Calcium influx inducing phospholipase enzyme to make IP3
- IP3 releases Ca from acrosome
- Elevated Ca triggers acrosomal releasefushion of the acrosomal vesicle w/ sperm cell mem (exocytosis) the extention of the acrosomal procress enzymes and proteosomes digest a path through the jelly coat adheres to vit envelope testies sperm to egg bindin in acrosome mem
globular -> actin microfilaments
The fast block to polyspermy in sea urchins is obtained by
- change in resting potential of the egg that is not compatible with fertilization
- Changing membrane potential from -70mV to +20mV
In the absence of hedgehog signal
Smoothened is degraded Ci (drosophila) and Gli (vertebrates) inhibitors are bound to DNA tethered to mictrotubles cleaved ->Ci acts as a repressor
Which one of the following receptor configurations is classic in Canonical Wnt signaling?
-Wnt canonical patway, or beta-catenin pathway, stabilizes b-catenin so that it enters the nucleus and associates with T cell factor, also known as LEF (lymphoid enhacer factor) to activate gene transcription
-Wnt binds to LRP5/6 and frizzled receptor changing LRP5/6’s conformation so that it binds Axin and GSK3 inside the cell. Frizzled binds Disheveled which locks the proteins bound to LRP5/6
Anoikis…
means apoptosis stimulated by loss of adhesion
Signals that lead to the formation of IP3 can ..
-cause a release of calcium from intracellular stores (Ca2+),
-release Ca2+ into the cytoplasm by opening the calcium channels of the endoplasmic reticulum.
slow block
Juxtacrine signals induce differential gene expression depending on how far are the cells from the
- cells/cellular receptor
Epithelium-mesenchymal induction experiments (frog-salamander transplants) proved that …
- it depends on juxtacrine signaling and that the ectoderm is what carries specific genetic information
- mesenchymal tissue run cross species barriers
- the ectoderm carries specific genetic programs
- response of epithelium in species specific
The sperm activating protein Rasact …
-Resact is species specific. Resact also acts as a sperm-activating peptide. Sperm-activating peptides cause dramatic and immediate increases in mitochondrial respiration and sperm motility. Resact is a chemotactic peptide
- isolated from egg jelly of sea urchin diffuses from jelly to sea water and attracts sperm to egg only attracts sperm from a puntulata not other species sperm binds to sperm recasct recptor activates quanylyl cyclase which prouduces more cGAMP that activates ca2+ channel in sperm tail