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