Fertilization Flashcards
What are layers in an invertebrate egg?
Jelly layer, viteline envelope, cell membrane, cortical granule layer, nucleus
What are layers in a vertebrate egg?
ECM with cumulus cells, zona pelucida, periviteline space, nucleus
What are the five steps of recognition between sperm and egg in invertebrates (sea urchins)?
- Sperm contacts jelly layer
- Acrosome reaction
- Digestion of the jelly layer
- Binding to viteline envelope
- fusion of acrosomal membrane to egg membrane
What are the five steps of recognition between sperm and egg in vertebrates (mouse)?
- Sperm activated by female reproduction tract
- Sperm binds to zona pelucida
- Acrosome reaction
- Sperm lyses hole in zona pelucida
- Sperm and egg membranes fuse
Define chemotaxis
Movement along a chemical gradient signal
How does chemotaxis work in sperm (sea urchin)?
The chemical sent from source binds to a receptor, turns on calcium influx, causes swimming in that direction
What two types of taxis are utilized to guide sperm to egg in vertebrates?
Chemotaxis and thermotaxis
What has a longer range, thermotaxis or chemotaxis?
thermotaxis
What is the name of the thermotactic receptor?
TRPM8
What are the muscular contractions of the female reproductive tract that push sperm closer to the egg?
Peristolsis
What is the role of lectin in the acrosome reaction in invertebrates?
Lectin receptors cover the outside of the sperm head. Molecules in the jelly layer fill the receptors, activating the acrosomal reaction
What is the role of acrosome enzymes in invertebrates?
To dissolve the jelly layer?
What is the role of the acrosome reaction?
- To dissolve the jelly layer
2. To extend an actin microfilament covered in bindin
What is the role of bindin in fertilization?
Species-specific recognition factor required for binding to viteline envelope
What is ZP3 in mammals?
A factor found in the zona pelucida of the egg that triggers the acrosomal reaction in the sperm
Is ZP3 the only factor that triggers acrosomal reaction and fertilization?
No. other interactions with sugars on the ZP3 have also been found to be of importance
After the acrosomal reaction has occurred in mammals, what is left of the sperm?
A covering filled with receptors for ZP1 and ZP2
Is ZP3 always required to get acrosome reaction?
No. It has been demonstrated.
What is the difference between fusion in vertebrates and fusion in invertebrates?
Invertebrates is like a missile hitting the ground: vertebrates is like a plane landing
Define fast block
OCCURS ONLY IN INVERTEBRATES!
Upon fertilization by first sperm, action potential goes over the entire egg, changing charge of surface and repelling sperm
Define slow block
- Also called cortical granule reaction
- Upon fertilization, cortical granules are released that form a barrier in the viteline layer.
- Dependent on Ca2+
- Occurs in both vertebrates and invertebrates
In mammals, what factor is required for slow block?
ZP2
What are roles of calcium influx in sea urchin egg fertilization? (4)
- slow block,
- Reinitiation of the cell cycle
- Formation of the hyaline layer
- Stimulation of protein synthesis, DNA rep, etc.
The cortical granule reaction creates what layer?
The hyaline layer
