Gametes and fertilisation 7 Flashcards
What happens in fertilisation?
Egg activation
Zygote formation
What type of fertilisation do sea urchins undergo?
External
Describe the acrosomal reaction of a sea urchin
Sperm contacts the eggs jelly
Acrosomal reaction: Hydrolytic enzymes released from the acrosome make holes in the jelly
Fusion of egg and sperm and egg membranes
Cortical reaction: cortical granules in the egg fuse with the plasma membrane
Entry of sperm nucleus
What is conspecific fertilisation?
Egg fertilised by sperm of same species
What happens in fast block to polyspermy?
Fusion of plasmamembranes Channels in egg plasmamembrane open Na+ influx from sea water Membrane depolarisation Change in plasmamembrane – no more sperm in
What are the 4 stages of oogenesis?
Oogonlum
Primary oocyte
Seconday oocyte
Ovum
What does ovulation release?
Secondary oocyte and the first polar body; both surrounded by the corn radiata
What is required for human fertilisation?
Sperm capacitation
What binds on initial mammalian sperm and egg contact?
zona pellucida ZP3 binds to 1-4-galactosyltransferase on sperm
What is released when mammalian sperm and egg come into contact?
Acrosomal contents
What digest zona pellucida glycoproteins?
Acrosin
-N-acetylglucosaminidase
Describe the process of sperm and egg interaction (mammalian)
zona pellucida ZP3 binds to 1-4-galactosyltransferase on sperm
acrosomal contents released
acrosin and -N-acetylglucosaminidase digest zona pellucida glycoproteins
fertilin on sperm head binds integrin-like protein and CD9
membrane fusion
Fast block to polyspermy (depolarisation)
Slow block to polyspermy
What is the role of acrsomal enzymes in fertilisation?
Create gaps in the corna radiata
