Fertilization Flashcards
Who invented the first microscope?
Antonie Philips van Leeuwenhoek
What 2 mechanisms prevent polyspermy?
- Slow block
2. Fast block
How does the fast block prevent polyspermy? Why is it not enough on its own? Do humans have it?
Outer membrane of egg depolarizes, preventing sperm binding. Doesn’t last very long and isn’t present in mammals.
How does the slow block prevent polyspermy? Why is it not enough on its own?
Cortical granules beneath egg surface release contents, causing the envelope to harden, swell, and delaminate, keeping sperm away. Not fast enough on its own in most cases (15-60 seconds to activate).
How is the slow block to polyspermy initiated?
By the release of calcium from the egg endoplasmic reticulum.
What 4 materials are released from cortical granules?
- Serine proteases
- Mucopolysaccharides
- Peroxidase/transglutaminase
- Hyalin
Why is polyspermy bad?
Can lead to polyploid offspring which are not viable.
What is digyny? What about diandry?
Meiosis defects leading to polyploidy
Digyny: a diploid oocyte
Diandry: a diploid sperm
What is the function of ZP1, ZP2, and ZP3 glycoproteins?
Form the matrix of the zona pellucida surrounding the oocyte.
______ receptor on sperm binds to ______ residues on ZP3. Induces the acrosome reaction
Galactosyltransferase receptor. N-acetylglucosamine residues.
What is the “cumulus layer”?
A layer of cells surrounding eggs. Pretty much invisible.
What is the function of bindin?
Allows species specificity for binding of sperm to egg. Localized in the acrosomal process of the sperm.
Describe the acrosome reaction.
The acrosomal vesicle exocytoses its contents (enzymes) which then fuse to the extending acrosomal process.
What is the “vitelline envelope”?
A fibrous, glycoprotein-containing mat surrounding the egg.
What is thermotaxis?
Increased temperature in the oviduct, leading sperm towards the egg.
