Flashcards in Lecture 09: Fertilization (Pozor) Deck (24):
sequence of events of sperm/oocyte interaction
1. occyte maturation to 2nd meiotic division, ovulation
2. sperm - capacitation, acrosome reaction
3. penetration of cumulus and zona pellucida
4. ionic changes, cortical granules release - block to polyspermy
5. meiotic resumption, 2nd polar body extruded
6. pronuclear formation
7. DNA synthesis
8. metabolic exchange
9. syngamy - merging haploid sets of chromsomes on mitotic spindle
definition of fertilization
the process by which the male and female gametes unite to form a single celled zygote
what is the ovulated oocyte surrounded by?
- cumulus oophorus
- zona pellucida (Z1, Z3, Z3)
- perivitelline space with first polar body
- viteline membrane
what is special about ZP3?
it will bind with receptors on membrane of sperm cell. without ZP3 there is no fertilization because sperm would not be able to penetrate through zona pellucida
zona pellucida glycoprotein 3 (ZP3)
a sperm receptor which binds zona binding receptor (ZBR) on newly exposed sperm head. Activates acrosome reaction promoting region (ARPR)
activation of ARPR causes what reaction to occur?
what do sperm do? what is their schtick? (they do 4 main things)
1. maturation in the epididymis
4. acrosome reaction
what is capacitation?
no change in sperm morphology it's just a motility change. a hyperactivation. they use more cAMP and increase power output
where does capacitation occur?
in the female repro tract, mostly in the isthmus of the oviduct
what causes capacitation to occur?
1. an increase in pH
2. changes in intracellular Ca
3. changes in the tail - hyperactivation
what is necessary for activation of the membrane signal transduction pathways of capacitation?
transfer of cholesterol to albumin
what is necessary for phosphorylation of proteins and polymerization of actin throughout capacitation?
activation of protein kinase A
what is necessary for hyperactive sperm motility in capacitation?
tyrosine phosphorylation of proteins
what is necessary for sperm penetration into the oocyte and decondensation of sperm DNA?
polymerizationof globular actin to filamentous actin
1) Fusion of the sperm plasma membrane with the outer acrosomal membrane
2)Desquamation (destroying) of sperm's outer membrane (inner membrane still intact)
3) enzymes spilled out of sperm cell which break down egg's coating and allow fertilization to take place
hydrolytic enzymes released during acrosome reaction
What is my Bella's favorite word?
sperm binds to it in secondary binding in zona pellucida after acrosomal reaction takes place. Helps to actively pull sperm into the oocyte
mechanisms within zona pellucida to block polyspermy:
1) cortical granules exocytosis and hardening of zona pellucida
2) modification of ZP3 and ZP2
Membrane (vitelline) block
changes in vitelline membrane polarization to block polyspermy
What hormone inhibits further meiosis after second arrest in metaphase II? ***
Maturation Promoting Factor (MPF)
What inhibits MPF and allows meiosis to resume after second arrest?
sudden influx of Ca
What must occur when sperm enters oocyte before fusion of DNA can occur?
decondensation of DNA into male and female pronuclei