Biology Assignment

Biology Assignment

Chapter 1-Oogenesis, Fertilization and Cleavage

Oogenesis

It is a process that involves prolonged interaction between the oocytes and their somatic accessory cells.

Major developmental stages in the egg development involve transformation of a miotic stem cell into an egg precursor that is meotically committed, transition from slowly growing vitellogenesis to a rapid accumulation of nutrients and at last, origin of a haploid genome resulted by a complete miotic division.

Proteins, Ribosome and Organelles required to start the developmental procedures are already present in the egg.

Factors in regions of the mature eggs that have NB roles in development are known as Morphogenetic determinants. These determinants are place asymmetrically in eggs cytoplasm as a result of the Differential gene expression starts in egg development.

Formation, growth & maturation of the female gamete begin in embryonic life.

Oogenic mechanics and pattern are different for different species.

Extensive loss of oocytes takes place during normal ovarian development in most animals where Oocyte demise involves PCD - apoptosis.

Death of germ cells is a prominent feature of mammalian ovary development.

In invertebrates, C. elegans - excess eggs die to donate their cytoplasm to the surviving eggs where as in Drosophila nurse eggs contract and cytoplasm flows into the oocyte - doubling of the volume

Attrition, the death of germ cells and Follicular Atresia, the death of follicular cells are the two Program Cell Death (PCD) categories.

Methods used to find Oogenic Cycles includes the mechanism of Histology or histochemistry, Immunocytochemistry, Molecular biology and direct anatomical observation of gonad maturity.

Previtellogenic, increasing ribosomes and Vitellogenic-lipogenic, accumulation of nutrients are the two egg development phases in animals.

In the Embryonic life is when Oogenesis begins in humans.

Fertilization

The process that involves the transfer of genes from parents to their offspring.

Combining the genes of the parents and reproduction are the two basic aims achieved by fertilization.

Egg-sperm interaction, regulation of sperm, pronuclei fusion, developmental phases of the egg and activation of both the gametes are the steps in fertilization.

Sperm recognition includes cheometric attraction between the sperm and the egg, release of enxymes by the acrosomal vesicles exocytosis, the sperm making its way through the ecxtracellular egg wall and finally fusion between the egg and cell membrane.

In sea urchins, fertilization starts with the concat of sperm with jelly layer, followed by acrosomal reaction, later followed by the digestion of jelly layer and then binding of the sperm with the vitelline envelop and at last fusion between the egg and the acrosomal membrane. In a mouse, the sperm activated by the female reproductive system is fuse with zona pellucid and after the acrosomal process the sperm penetrates through the zona where then the sperm and the egg membrane are fused.

The extra coating is provided to the egg to prevent the fusion of another sperm in Cortical Reaction.

The cortial reaction in sea urchins includes Cortical Reaction in Sea Urchins Vesicles containing enzymes and other molecules - released when sperm bind membrane Products contribute to the egg extra-cellular matrix and fertilization envelope.

Acrosomes, which were the result of fusion of acrosomal ...