Chapter 7- Fertilization

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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

2
Transformation from germ cell to sperm
Germ cell
_________ Derived from centriole
____________
____________
Nucleus is ______
Derived from ______
Fig. 7.2
Mature sperm
3
Sperm __________
____________ doublet
A cross-section
Fig. 7.3
A single microtubule

• Microtubules are composed of _______
• Sperm ___________ provided by______
• Dynein is attached to microtubule doublet
• Dynein hydrolyzes ___ to bend ________
• Human disease- no dynein _________

4
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
Egg meets sperm
5 steps
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
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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
  _________________

7
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

8
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 _________________

9
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
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Egg meets sperm
___________ is key!
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
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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 __________________

12
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
13
Molecular details of PIP3 signaling
____
____________
Phosphatidyl-inositol 4,5 bisphosphate _____
Inositol 1,4,5 triphosphate _____
Fig. 7.28
14
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
0
100
Fig. 7.31
800
Time (secs)