The cell cycle is a series of phases that a cell goes through as it grows and divides. It is typically divided into several main processes, which can be grouped into two main stages: interphase and the mitotic phase (M phase). Here are the main processes involved:
1. Interphase:
Interphase is where the cell spends the majority of its life. It is further divided into three sub-phases:
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G1 phase (Gap 1): The cell grows in size, synthesizes mRNA and proteins, and makes sure the environment is favorable for DNA replication. It also carries out normal metabolic processes.
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S phase (Synthesis): The cell replicates its DNA, so each chromosome consists of two sister chromatids. This ensures that each daughter cell will receive an identical set of chromosomes during division.
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G2 phase (Gap 2): The cell continues to grow and produces proteins necessary for cell division. It also makes final preparations for mitosis, including the synthesis of microtubules.
2. Mitotic Phase (M phase):
This phase includes the processes of mitosis and cytokinesis:
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Mitosis: This is the process by which the cell's nucleus divides. It is further divided into several stages:
- Prophase: Chromatin condenses into visible chromosomes, the nuclear envelope breaks down, and the mitotic spindle begins to form.
- Metaphase: Chromosomes align at the metaphase plate (the cell's equatorial plane).
- Anaphase: Sister chromatids separate and are pulled to opposite poles of the cell.
- Telophase: The chromosomes reach the poles, the nuclear envelope re-forms around each set of chromosomes, and chromosomes begin to uncoil back into chromatin.
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Cytokinesis: This is the process that follows mitosis, where the cytoplasm divides, resulting in two separate daughter cells. In animal cells, this is often achieved by a contractile ring forming an indentation at the center of the cell (cleavage furrow), while in plant cells, a cell plate forms to separate the two daughter cells.
Regulation:
The cell cycle is tightly regulated by a series of checkpoints (G1, G2, and M checkpoints) that monitor the cycle's progression and ensure that errors (such as DNA damage) are corrected before the cell proceeds to the next phase.
These main processes ensure proper cell division and replication, which are essential for growth, development, and tissue repair in multicellular organisms.
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