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:
Describe the events of the cell cycle, including interphase, mitosis, and cytokinesis.
The cell cycle is the ordered sequence of events that occur in a cell in preparation for cell division. The cell cycle is a four-stage process in which the cell increases in size, copies its DNA, prepares to divide, and divides.
The cell cycle is divided into the following events:
1. Interphase: Interphase is the portion of the cell cycle that is not accompanied by observable changes under the microscope, and includes the G1, S, and G2 phases. During interphase, the cell grows, replicates its DNA, and prepares for mitosis.
a. G0 phase: The G0 phase or resting phase is a period in the cell cycle in which cells exist in a quiescent state. It is the phase, where the cell is neither dividing nor preparing to divide. It is a distinct quiescent stage that occurs outside of the cell cycle.
b. G1 phase: G1 is an intermediate phase occupying the time between the end of cell division in mitosis and the beginning of DNA replication during the S phase. During this time, the cell grows in preparation for DNA replication, and certain intracellular components undergo replication.
c. S phase: S phase is the phase of the cell cycle in which DNA is replicated. It occurs between the G1 phase and the G2 phase. The processes that occur during S-phase are tightly regulated and widely conserved.
d. G2 phase: G2 phase is a period of rapid cell growth and protein synthesis during which the cell prepares itself for mitosis. It is not a necessary part of the cell cycle, as some cell types proceed directly from DNA replication to mitosis.
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