w3_fertilization.pdf - Fertilization Fertilization Fusion of gametes to start creation of a new individual 4 major events of fertilization(1 Contact and

w3_fertilization.pdf - Fertilization Fertilization Fusion...

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Fertilization
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Fertilization : Fusion of gametes to start creation of a new individual 4 major events of fertilization: (1) Contact and recognition between sperm and egg. (ensure same species) (2) Regulation of sperm entry into the egg. (ensure only one sperm unites with egg nucleus) (3) Fusion of genetic material of sperm and egg. (4) Activation of egg metabolism to start development. 2/76 Fertilization
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Sperm Developmental Biology, 9/e, Scott F. Gilbert, Chapter 4 Homunculus, 1694 17 th century parasitic animal living in semen. contains preformed embryo female only provides a nutrient soil for sperm 18 th century sperm needs to touch the egg to form the embryo (semen filtration) sperm is a parasite egg contains the embryo but needs sperm fluid to start growing 19 th century sperm universally exists in sexually mature (young) males doubt on the idea that a normal semen can contain such an enormous number of parasites! Sperm-egg communication = magnet/iron communication (1840) Sperm enters egg and the nuclei unite (1876, sea urchin) 3/76 Fertilization
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Sperm Digestive enzymes (proteins and complex sugars) (Acrosome) Globular actins extending to form acrosomal process for sperm/egg recognition (some species) 4/76 Fertilization
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Sperm Developmental Biology, 9/e, Scott F. Gilbert, Chapter 4 Condensed (6 fold more compact than metaphase chromosomes) (acrosome) 5/76 Fertilization
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Sperm Nucleus Mitochondria Tubulin Pro-acrosin - GFP Bull sperm Mouse sperm 6/76 Fertilization
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Sperm - Axoneme Axoneme is the major motor protein of the flagellum. Formed by microtubules emanating from centriole. This structure is conserved throughout the eukaryotic kingdom. 7/76 Fertilization
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Sperm - Axoneme Dynein ATPase generates the energy that allows the active sliding of the outer doublets causing the flagellum to bend. Kartagener triad syndrome absence of functional dyneins. ATP comes from the midpiece of the sperm. Mammalian sperms can move when they are released after ejaculation but they are not mature . Mammalian sperms need to undergo another maturation, capacitation , in female genital tract to be able to bind and fertilize the egg. Developmental Biology, 9/e, Scott F. Gilbert, Chapter 4 Protofilaments made of tubulin 8/76 Fertilization
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The egg (ovum) Developing egg ( oocyte ) not only conserves its cytoplasmic material but also accumulates more. In contrast sperm loses most of its cytoplasmic components. All the materials necessary for the beginning of the development must be stored in the egg. egg 10,000 times larger than its sperm. Sea urchin 9/76 Fertilization
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