Chapter 7- Fertilization More historical perspective Late _____- _______________- sperm are parasites? Late ______- _____________- Sperm are still parasites? Early ______- ________- Sperm contribute to fertilization Late _____- Hertwig and Fol show sperm entering egg, union of _____________ observed

Transformation from germ cell to sperm _________ Derived from centriole ____________ ____________ Nucleus is ______ Derived from ______ Mature sperm Fig. 7.2

Sperm __________ ____________ doublet 2 central microtubules Fig. 7.3 A cross-section A single microtubule Microtubules are composed of _______ Sperm ___________ provided by______ Dynein is attached to microtubule doublet Dynein hydrolyzes ___ to bend ________ Human disease- no dynein = _________

The egg- loaded with proteins, ribosomes, ______________________________ protective chemicals (in sea urchin) ______________ (a fibrous mat)- ~8 proteins Plasma membrane A ____________ in mammals Nucleus _________- a mass of ovarian follicular cells (in mammals) Fig. 7.4- Sea urchin egg Fig. 7.7- Mammal egg

5 steps Egg meets sperm 1. Sperm ______________ Many species use _________________- (migration following a __________________________) Example- _______ is a 14 AA peptide that attracts sperm in the ___________ Before After Point of _____ injection In mammals, sperm must be ______________prior to fertilization

5 steps Egg meets sperm 2. ______________ reaction a. Sperm contacts ___________ b. _________________ starts and digests jelly layer c. Binding to _________ envelope d. Fusion of acrosomal process with _________________

4 steps Egg meets sperm 3. Binding to vitelline layer (or _________ ________________) a. Sea urchin- _________ protein mediates species _____________ and binds to _________ on egg vitelline layer b. In mice, the protein ____ is the sperm ____________ on zona pellucida ZP3 also ___________ the acrosomal reaction A second protein, _____, mediates __________ after the acrosomal reaction

4 steps Egg meets sperm 4. Fusion of ______ and ________ plasma membranes Membranes fuse, a ____________________ is formed, and entire sperm enters egg In mammals, ___________(in the sperm membrane) is essential for ___________ _____________ is bad Normally, egg and sperm nuclei fuse to create _________ nucleus and single _____________ If two sperm enter-_____________ and messed up division by _________________

Egg meets sperm Solutions to __________________ 1. ____________- change __________________ of egg membrane Rapid influx of___________ ions (within 1-3 seconds) post sperm binding Sperm can no longer ____ with egg membrane Effect only lasts a _________________ 2. ____________- removal of remaining attached _________. In sea urchin 15,000 _______________ fuse with egg membrane, and clip off ___________, releasing attached sperm See Sea urchin movie Cortical granules

Egg meets sperm ___________ is key! Sperm Egg Fertilized Egg What initiates the ____________ reaction?? Sperm Egg Fertilized Egg [Ca++] ___ ______ A wave of calcium is released from the _________ ________ that is complete in 30 ________ Sperm entry 15sec 30sec Fig. 7.25- Sea urchin

____ is from mostly from ________ ________ in snails and worms) Egg meets sperm What ___________the cortical ___________ reaction?? ____ is from mostly from ________ ________ in snails and worms) If block calcium with a ________ (e.g.EDTA)- block _________________ reaction Membrane _______________ Cell __________________

Calcium release pathway Binding receptor activates a _________ ____________ which activates ____, which splits PIP2 into DAG and IP3, which activates _____ channel ________________ (PLC) ____+_____ PIP3 Acrosomal process Plasma membrane Cytoplasm Nuclear membrane Fig. 7.29B

Molecular details of PIP3 signaling ____ ____________ Phosphatidyl-inositol 4,5 bisphosphate _____ Inositol 1,4,5 triphosphate _____ Fig. 7.28

Nuclear fusion events in sea urchin When Sperm enters egg- ______________ and __________ disintegrate ______________ partially degrades, and sperm chromatin ______________ (relaxes) _________extends microtubles in egg and contacts female ____________ Nuclei migrate together and fuse to form ______________ _____ pronucleus At this stage – we use the terms ________ _________ and _____ ______________. _______ pronucleus 100 800 Fig. 7.31 Time (secs)