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MILITA ROYMILITA ROYBEJOY NARAYAN MAHAVIDYALAYABEJOY NARAYAN MAHAVIDYALAYA
SPERM FORMATIONMaturation of a sperm cell- 1. Nucleus is condensed
2. Acrosome is formed
3. Neck piece and tail piece is formed:formation of flagellum from centriole
Body elongated and become streamlined bydiscarding the excess cytoplasmic material
Ultrastructure of flagella:Flagella contribute to sperm motility
protofilaments consist of tublulin dimers histone H1 stabilizes flagellar microtubules dynein, attached to microtubules hydrolyzes ATP, ATP comes from mitocondria in
midpiece sliding of outer doublet
EggEgg attain the large size due to accumulation ofthe following necessary materials yolk proteins ribosomes t-RNA m-RNA morphogenic factors protective chemicals
Egg attain the large size due to accumulation ofthe following necessary materials yolk proteins ribosomes t-RNA m-RNA morphogenic factors protective chemicals
Some of the structural components of theamphibian eggJelly coatVitelline envelopeCortical granuleMitochondriaYolk
Some of the structural components of theamphibian eggJelly coatVitelline envelopeCortical granuleMitochondriaYolk
Sperm enters at various stages of meiotics division of theegg of different animals
Sperm AttractionChemotaxis
Movement toward a chemical, gradient is followed In Arbacia punctulata – the effects of adding resact to sperm suspension resact isolated from egg jelly is depicted in the picture
12 3 4
Sperm AttractionWhat is a sperm-activating peptide? RESACT- the 14 peptide amino acid is responsible for
chemotaxis. Causes increases in sperm respirationand motility via a signal transduction mechanism.
What is a sperm-activating peptide? RESACT- the 14 peptide amino acid is responsible for
chemotaxis. Causes increases in sperm respirationand motility via a signal transduction mechanism.
Sperm – Egg InteractionThe acrosomal reaction in sea urchins: Acrosomalmembrane is fused with the sperm plasmamembrane , enzymes are released.
Components of egg jelly bind to receptors on spermcell membrane Calcium channels opened, calcium enters sperm head
and induces fusion of acrosomal vesicle withmembrane leading to exocytosis of enzymes Acrosomal process forms from polymerization of
actin also facilitated by calcium
Components of egg jelly bind to receptors on spermcell membrane Calcium channels opened, calcium enters sperm head
and induces fusion of acrosomal vesicle withmembrane leading to exocytosis of enzymes Acrosomal process forms from polymerization of
actin also facilitated by calcium
Sperm – Egg InteractionThe bindin protein(present on the innermembrane ofacrosome) are now atthe tip of the spermand plays an importantrole in species specificrecognition.
The bindin protein(present on the innermembrane ofacrosome) are now atthe tip of the spermand plays an importantrole in species specificrecognition.
Sperm – Egg Interaction Polymerization of egg actin leads to formation of
fertilization cone, helps for fusion.
Sperm – Egg Interactionin mammals contactoccurs on side ofsperm head; CD9associated integrinprotein in eggneeded for fusionalong with fertilin insperm
in mammals contactoccurs on side ofsperm head; CD9associated integrinprotein in eggneeded for fusionalong with fertilin insperm
Preventing Polyspermy Why is polyspermy a problem?
Preventing Polyspermy
Preventing PolyspermyFertilization membrane is formed from the fusionof Cortical granules with the plasma membrane ofegg. The internal enzymes ( such asHyaleuronidase, Peroxidase) and hyalin arereleased which form the membrane. Themembrane is a permanent structure and apermanent solution to the problem of polyspermy.
Fertilization membrane is formed from the fusionof Cortical granules with the plasma membrane ofegg. The internal enzymes ( such asHyaleuronidase, Peroxidase) and hyalin arereleased which form the membrane. Themembrane is a permanent structure and apermanent solution to the problem of polyspermy.
Egg Activation increase in calcium levels trigger many reactions – can
block with EGTA can activate artificially using calcium ionophore most protein synthesis comes from stored mRNA by
removing an inhibitor
increase in calcium levels trigger many reactions – canblock with EGTA can activate artificially using calcium ionophore most protein synthesis comes from stored mRNA by
removing an inhibitor
Egg Activation signaling pathway releases intracellular calcium
ion concentration
Fusion of Genetic Material DNA & centriole forms initial spindle for division.
sperm nucleus decondensed to form pronucleus –involves phosphorylation of lamin protein in envelopand two sperm histones can fuse with egg pronucleus.
lengthy process – sperm DNA bound to protamines incompacted form – glutathione breaks dissulfide bondsto de-compact DNA; when sperm enters egg hasn’tcomplete meiosis; DNA synthesis occurs separately ineach pronucleus; true diploid nucleus doesn’t formuntill 2-cell stage
DNA & centriole forms initial spindle for division.
sperm nucleus decondensed to form pronucleus –involves phosphorylation of lamin protein in envelopand two sperm histones can fuse with egg pronucleus.
lengthy process – sperm DNA bound to protamines incompacted form – glutathione breaks dissulfide bondsto de-compact DNA; when sperm enters egg hasn’tcomplete meiosis; DNA synthesis occurs separately ineach pronucleus; true diploid nucleus doesn’t formuntill 2-cell stage
Rearrangement of Egg Cytoplasm Cytoplamic rearrangement occurs as a result of
fertilization : Parallel microtubles between corticaland inner cytoplasm appear responsible formovement
Cytoplamic rearrangement occurs as a result offertilization : Parallel microtubles between corticaland inner cytoplasm appear responsible formovement