fertilisation Flashcards
what two processes need to occur before fertilisation
capacitation and the acrosomal reaction
what cells release retinoic acid
sertoli cells
what does retinoic acid do before fertilisation in males
directs the sequential programs of spermatonogonial differentiation and meiotic differentiation
what stage do oocytes get paused at in the ovaries
4n (diplotene) stage of meiosis as primary oocytes (~3months gestation)
~1000 PGCs produce ___________ oogonia in gestation but most ______
7million oogonia but most die
what is the difference between male and female meiotic divisions
female meiotic divisions are asymmetric and male are symmetric
what is the model organism most often used to study fertilisation
sea urchin
what is the fast block to polyspermy
oocytes membrane depolarisation
what is the slow block to polyspermy
a wave of Ca2+ across egg causing cortical granules to release content that deactivated the ZP3 receptors making the zona pellucida impermeable
what is the Calcium increase caused by
PLCzeta (a sperm protein)
what does do calcium at fertilisation
- trigger for egg activation
- activates calmodulin dependent protein kinase 2
- triggers degradation of proteins keeping egg arrested
- triggers release of cortical granules to block additional sperm entry
how does PLCzeta cause calcium release
- plc zeta hydrolyses PIP3 generating IP3 and DAG
- IP3 diffuses info cytoplasm and binds to receptor on endoplasmic reticulum
- release of calcium ions into cytoplasm
what is the polyspermy block at the plasma membrane caused by EGG-SPERM receptor system
Izumo1 is tethered to sperm membrane, forms an adhesion complex with its receptor protein Juno, on egg membrane. after fertilisation juno is lost via vesicles
fertilisation doesn’t take place without this complex
