Exam 1 Flashcards
Phylotypic Stage
A period in development in a animal when it most closely resembles other species in its phylum
Egg v. Ovum v. Oocyte
Ovum - mature egg
Oocyte - developing egg cell
Jelly Layer
Extracellular matrix that surrounds sea urchin eggs. Contains polysaccharides that are species specific.
Vitelline Envelope
Extracellular matrix that forms a fibrous mat around the egg outside the cell membrane. During fertilization the VE undergoes a series of changes that result in the fertilization envelope.
Chemotaxis
Oriented movement of cell/organism in response to external chemical signals
Acrosome/Acrosomal vesicle
Caplike organelle that is inside the sperm head. Contains proteolytic enzymes that can digest the extracellular coats surrounding the egg, allowing the sperm to gain access to the egg cell membrane for fusion
Acrosome Reaction
Egg polysaccharides in jelly bind to sperm receptors. Ca++ channels open, Na+ influx / H+ epplux, Phospholipase enzyme releases secondary messenger.
Role of Sulfated Polysaccharides
Trigger acrosome reaction, species specific
Exocytosis
A form of active transport where the cell transports molecules out of the cell
G-actin pool
polymerization of actin forms fertilization cone
Polyspermy
Multiple sperm trying to fertilize
Fast Block to Polyspermy
Electrical
Fast (1-3 sec)
Transient (60 sec)
1. Prior to sperm binding, Ca++ channels in egg membrane are closed
2. When Bindin proteins on sperm match to the egg receptors, the sodium channels open
3. An influx of sodium ions enters the egg
3. Acrosomal reaction begins and sodium channels close - depolarization of egg cell
Slow Block to Polyspermy
Slow (30-60 sec)
Permanent
Cortical Granule Reaction
1. Sperm release soluble factors, which triggers the tyrosine kinase
2. TK -> PLC
3. PIP2 goes through channel which creates IP3
4. IP3 opens Ca channel from the ER
5. CA now in cell causes exocytosis of cortical granules
6. Exocytosis causes release of CGSP and other proteins, creating fertilization envelope
Blastula
Cells in blastomere form a hollow sphere around central cavity.
Cell Movements
-Ingression
-Convergent Extension
-Invagination
- Migration of individual cells from the surface layer into the interior of the embryo
- Mechanism for elongation
- The indenting of a region of cells
Gastrulation
Movement and rearrangement of blastomeres to form the three germ layers that will comprise the embryo - ectoderm, endoderm, mesoderm
RNA in situ hybridation
A technique used to visualize the location of specific messenger RNA transcripts within a sea urchin egg or early embryo at the time of fertilization.
Blastomere Recombination Experiment
Researchers isolate individual blastomeres from an embryo at the early cleavage stages. Cell fate and cell interaction
Filopodia
Long thin processes containing microfilaments
Canonical WNT Signaling Pathway
Cell signaling mechanisms
-paracrine
-autocrine
-juxtacrine
- A secreted protein that signals between cells of long distances
- The same cells that secrete paracrine factors also respond to them
-Signaling between cells that are in direct contact with one another
Double Negative Gate
Uses two repressor to control gene expression in a specific pattern
Animal pole
The pole of the egg or embryo where the concentration of yolk is low
Vegetal pole
The pole of the egg or embryo where the concentration of yolk is high
MBT / MZT
EMT
Phospholipase C
Soluble factors that activate tyrosine kinase and IP3 pathway - results in CA++ release and activation of the egg
PIP2
IP3
A second messenger generated by Phospholipase C that releases extracellular CA++ stores. Important in the initiation of both cortical granule release and sea urchin development
Holoblastic Cleavage
Complete Cleavage
Isolecithal
Sparse, evenly distributed yolk
-Radial (sea urchin)
-Spiral
-Bilateral
-Rotational (mammals)
Mesolecithal
Moderate vegetal yolk diposition
Amphibians
Meroblasic Cleavage
Incomplete cleavage
Teloecithal (meroblastic)
Dense yolk throughout most of cell (fish reptiles)
Centrolecithal (meroblasitc)
Yolk in center of egg
- insects
