Biology 2581B Lecture Notes - Lecture 17: Zona Pellucida, Asymmetric Cell Division, Zp3
2 May 2020
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Document Summary
The development of multicellular organisms starts with two haploid germ cells; the egg/oocyte and the sperm. In the process called fertilization, they combine to create a diploid zygote cell. A membrane-bound compartment called the acrosome at the sperm"s tip contains soluble enzymes, including hydrolases and proteases, which are released close to the oocyte and digest the multiple egg surface layers. The first sperm to reach the egg fuses with the membrane and triggers a dramatic response by the oocyte. The sperm nucleus then enters the egg cytoplasm and both nuclei fuse. The oocyte contains necessary mitochondria and mrna transcripts of genes essential for the earliest stages of development. The formation of working tissues and organs depends on specific patterns of mitotic cell divisions, giving rise to cell lineages as cells differentiate into specialized cell types, meaning they become more restricted in their developmental potential.
