Oogenesis
The formation of the ovum (mature female gamete) from undifferentiated germ cells is called oogenesis. This process takes place in the ovaries (female gonads). Oogenesis consists of three stages known as the multiplication phase, growth phase, and maturation phase.
Cell Division
Cell division involves the formation of new daughter cells from the parent cells. It is a part of the cell cycle that takes place in both prokaryotic and eukaryotic organisms. Cell division is required for three main reasons:
What happens to the ends of linear chromosomes in eukaryotes during replication?
How are the ends of eukaryotic chromosomes maintained? What happens when
the process goes wrong?
DNA replication in eukaryotes is a highly regulated process and usually requires extracellular signals to coordinate the specialized cell divisions in different tissues of multicellular organisms. External signals are delivered to cells during the G1 phase of the cell cycle and activate the synthesis of cyclins. Cyclins form complexes with cyclin dependent kinases, which, in turn, stimulate the synthesis of S phase proteins such as DNA polymerases and thymidylate synthase. These complexes prepare cells for DNA replication during the S phase.
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