2 Embryo

Front 1

Fertilization

Back 1

Starts with the approach of the sperm to the egg and ends with he formation of diploid zygote

Front 2

Fertiliation Functions

Back 2

1. To transmit genes from parents to offspring

2. To initiate certain reactions in the egg cytoplasm which will allow the development to proceed

Front 3

Mechanisms to ensure that sperm and egg come together

Back 3

1. Production of excess gametes

2. Seasonal reproductive activity and gamete production

3. Behavioral/ mating modifications

4. External/ internal fertilization

If internal - path towards the female reproductive tract

Front 4

Germ cell forming sperm

Back 4

Haploid pronucleus - condensed DNA

Centriole produced flagellum

Golgi forms acrosomal vesicle which degrades egg covering

Mitochondria collect around flagellum

Cytoplasm expelled

Front 5

Axoneme

Back 5

Motor portion of a sperm

dynein - ATPases

9+2 microtubules

Front 6

Oocyte

Back 6

Developing egg

Diploid

Front 7

Ovum

Back 7

Developed egg - stage in meisosis where it could get fertilized

At the time of fertilization can be haploid or diploid depending on the species

Sperm and eggs are haploid

Front 8

Sea urchin as an experimental model

Back 8

sexually mature throughout year

produces many, large, transparent eggs

Toxopneustes livids

Front 9

Jelly layer

Back 9

Glycoprotein matrix - sperm attraction and activation

Front 10

Vitelline envelope

Back 10

Sperm egg recognition

Invertabrates

Front 11

Cortex

Back 11

gel like shell, under cell membrane, high globular actin, polymerizes into microfilaments after fertilization

Microfilaments help with cell division and sperm entry

Front 12

Cortical granules

Back 12

Prevent additional sperm entry after fertilization

Front 13

Cumulus

mammal

Back 13

Ovarian follicular cells

Nurture egg

Front 14

Corona

mammal

Back 14

Innermost layer of cumulus

Adjacent to the zona pellucida

Front 15

zona pellucida

mammal

Back 15

analog of vitelline envelope

Site for binding of sperm to oocyte

main barrier to interspecies fertilization and polyspermy

Front 16

Sea urchin sperm entry

Back 16

1. Sperm contacts jelly layer

2. Acrosome reaction

3. Digestion of jelly layer

4. Binding to vitelline envelope

5. Fusion of acrosomal process membrane and egg membrane

Front 17

Mammal sperm entry

Back 17

1. Sperm activated by female reproductive tract

2. Sperm binds to zona pellucida

3. Acrosome reaction

4. Sperm lyses hold in zona

5. Sperm and egg membranes fuse

Front 18

Conservation of egg cytoplasm

Back 18

Proteins

Ribosomes/tRNAS

mRNA

Morphogenic factors

Protective chemicals

Front 19

Fertilization major events

Back 19

1. Contact recognition

2. Regulation of sperm entry into the egg

3. Activation of egg metabolism to start development

4. Fusion of genetic material

Front 20

Contact Recognition and regulation of sperm entry

Step 2,3,4 can be reversed

Back 20

1. Chemoattraction

2. Exocytosis of acrosomal vessicle

3. Building sperm to extracellular envelope

4. Sperm through external layers

5. Fusion of sperm and egg membranes

Front 21

Sea urchin chemoattraction

Back 21

External fertilization

Only fertilize same species

Resact from egg jelly detected by sperm receptors which swim up gradient

Front 22

Resact binds to sperm, Ca2+ channel activated

Back 22

Ca2+ from sea water gets into cell and activates mitochondrial ATP apparatus and sperm flagellar dynein

Energy to swim

Front 23

Acrosome reaction - sea urchin

Back 23

1. Fusion of acrosomal vesicle to sperm cell

membrane

2. Extension of the acrosomal process

Front 24

Sperm Recognition

Back 24

acrosomal process contains bindin protein and egg cell has ERB1

Species specific

aka agglutination

Front 25

Female reproductive tract

Back 25

Non passive

Regulates transport and maturity of both gametes

Fimbriae of oviduct - "pick up complex"

Ciliary beating and muscle contractions move oocyte into ampulla region where fertilization takes place

Front 26

Femal reproductive tract- role of sperm

Back 26

flagellar action is minor in getting sperm to ampula

Sperm activity improtant when close to oocyte, must pass through cumulus

Directional cues form temp and chemical gradients

Front 27

Capacitation - mammal

Back 27

set of physiological changes and the molecular events mostly involve sperm cell membrane

bicarbonate ions in female tract cause loss of membrane cholesterol and changes in membrane proteins

Membrane hyperpolarization and increase in intracellular Ca2+ and pH

Front 28

Sperm competence

Back 28

Acquired when reaching the ampulla

Lost if there too long

6 day period after ovulation

After capacitated can sense temp gradient between isthmus and ampulla

Front 29

Two things necessary for fertilization

Back 29

Egg/ cumulus cells must producte chemotaxic molecules

Sperm capacitation

Front 30

Sperm recognition mammals

Back 30

Zona pelucida; zp1, zp2, zp3, accessory proteins

Reaction between zona and sperm regulate sperm binding

1. weak binding to oviduct derived ligand

2. sperm SED1 binds to ZP complex

2. sperm GaIT binds to ZP3 which initiates acrosomal reaction by opening Ca2+ chanels

Front 31

Acrosome reaction sea urchin vs mammal

Back 31

happens in both but only sea urchin has acrosome process

Front 32

Membrane fusion - mammal

Back 32

Sperm binds at side not tip

Dependent on expression of CD9 on egg and lzumo on sperm

May be other binding systems

Front 33

Prevention of polyspermy

Back 33

Causes incorrect number of chromosomes and incorrect number of centrioles

Fast block/ slow block

Some organisms such as salamanders do not prevent polyspermy

Front 34

Sea urchin fast block

Back 34

Changing electrical potential of egg cell membrane, 1-3 seconds

-70 low Na+ to +20 high

Transient mechanisms

Amphibians use Ca2+ channels

Probably doesn't happen in mammals

Front 35

Sea urchin slow block

Back 35

Cortical granule reaction, activated a minute after fusion

Granule enzymes modify extracellular space between zona pelucida and cell membrane

Front 36

Sea urchin slow block

Formation of fertilization envelope

Back 36

1. serine protease - digests protein posts in extracellular space, digests bindin receptors, clips off sperm

2. mucopolysaccharides - osmotic gradient, water enters and expands envelope

3. Peroxidase enzymes - harden envelope by cross linking tyrosine residues

4. hyalin coating forms around egg

Front 37

Polyspermy mammals

Back 37

Fast block not detected

Slow block - N-acetyl enzymes cleave off ZP3

ZP2 clipped by proteases from cortical granules which sheds bound unfused sperm

Front 38

Granule fusion in both mammals and sea urchins

Back 38

Driven by Ca2+ waves

Positive feedback to release more Ca2+

Front 39

Egg activation

Back 39

Egg is metabolically slow until sperm activation

Independent of fusion of genetic material

Early/late phase

Mammals have several waves of Ca2+ release

Front 40

IP3

Back 40

Inositol 1,4,5 triphosphate mediates Ca release from ER

Front 41

PLC

Back 41

phospholypase C

Front 42

DAG

Back 42

diacylglycerol - mediate a ph rise in egg

Front 43

Early phase

Back 43

Simultaneous as slow block polyspermy

Sea urchin- transient increase in Ca2+

Mammals - several waves release

Front 44

Ca2+ activates NAD+ kinase

Back 44

converts NAD+ to NADP+ which is a coenzyme involved in lipid biosynthesis

Front 45

Oxygen reduction to hydrogen peroxide

Back 45

important for crosslinking fertilization envelope in sea urchin

Free radicals cause DNA damage in egg - removed by glutathione and ovothiols

Front 46

Late phase activation

Back 46

Ca increase inhibits MAP kinase - DNA replication starts

Cyclin B production combines with cdk1 into mitosis promoting factor

Front 47

Sea urchin late phase

Back 47

synthesis of DNA and proteins dependent on pH increase. Na exchange for H+

Protein synthesis up-regulated quickly, independent of RNA synthesis - uses mRNA already present

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Back 48