Chapter 7- Fertilization

• 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

More historical perspective

Transformation from germ cell to

sperm

Fig. 7.2Derived from ______

Nucleus is ______

____________

_________Derived from centriole

Germ cell

Mature sperm

____________

Sperm __________

A cross-sectionFig. 7.3

____________ doublet

2 central microtubules

Microtubules are composed of _______Sperm ___________ provided by______

•Dynein is attached to microtubule doublet•Dynein hydrolyzes ___ to bend ________•Human disease- no dynein = _________

A single microtubule

The egg- loaded with proteins, ribosomes, ______________________________ protective chemicals

Fig. 7.4- Sea urchin egg

Nucleus

Plasma membrane

______________ (a fibrous mat)- ~8 proteins_____________ (in sea urchin)

Fig. 7.7- Mammal egg

A ____________ in mammals

_________- a mass of ovarian follicular cells(in mammals)

Egg meets sperm1. Sperm ______________

Many species use _________________- (migration following a __________________________)

Example- _______ is a 14 AA peptide that attracts sperm in the ___________

Before AfterPoint of _____ injection

In mammals, sperm must be ______________prior to fertilization

5 steps

Egg meets sperm

2. ______________ reaction

5 steps

a. Sperm contacts ___________

b. _________________ starts and digests jelly layer

c. Binding to _________ envelope

d. Fusion of acrosomal process with _________________

Egg meets sperm

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 steps3. Binding to vitelline layer (or _________________________)

a. Sea urchin- _________ protein mediates species _____________ and binds to _________ on egg vitelline layer

Egg meets sperm4. 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 _________________

4 steps

Egg meets spermSolutions 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

Cortical granules

See Sea urchin movie

Egg meets spermWhat initiates the ____________ reaction??

___________ is key!

EggSperm

[Ca++] ___ ______Fertilized Egg

A wave of calcium is released from the _________________ that is complete in 30 ________

30sec

Sperm entry 15sec

Fig. 7.25- Sea urchin

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

PIP3 ____+_____

________________ (PLC)

Fig. 7.29B

Acrosomal process

Plasma membrane

Cytoplasm

Nuclear membrane

Binding receptor activates a _____________________ which activates ____, which splits PIP2 into DAG and IP3, which activates _____ channel

Fig. 7.28

Molecular details of PIP3 signaling

Phosphatidyl-inositol 4,5 bisphosphate

_____

____________

Inositol 1,4,5 triphosphate _____

____

Nuclear fusion events in sea urchinWhen 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

Fig. 7.31 Time (secs)

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