The cell cycle is a series of events that takes place in a cell leading to its division and replication. It consists of several phases, which are generally divided into two main stages: interphase and mitosis.
Interphase
Interphase is the longest phase of the cell cycle, during which the cell prepares for division. It is subdivided into three specific phases:
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G1 Phase (Gap 1): This phase follows cell division. During G1, the cell grows and carries out normal functions. The cell synthesizes proteins and organelles, and it also increases in size. The G1 checkpoint checks for DNA damage and ensures the cell is ready for DNA synthesis.
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S Phase (Synthesis): In this phase, DNA replication occurs. Each chromosome is replicated to form two sister chromatids. The cell also continues to grow and produce proteins necessary for cell division.
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G2 Phase (Gap 2): After DNA has been replicated, the cell enters G2. Here, the cell continues to grow and produce more proteins. It also undergoes a final check of its DNA to ensure there are no errors before entering mitosis. The G2 checkpoint checks for DNA damage and ensures all DNA is replicated accurately.
Mitosis
Mitosis is the process of nuclear division, which is further divided into several phases:
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Prophase: Chromatin condenses into visible chromosomes, consisting of two sister chromatids joined at the centromere. The nuclear envelope begins to break down, and the mitotic spindle starts to form.
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Metaphase: The chromosomes align along the metaphase plate (the cell's equatorial plane) due to the action of the spindle fibers.
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Anaphase: The sister chromatids are pulled apart to opposite poles of the cell as the spindle fibers shorten.
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Telophase: The chromosomes reach the opposite poles and begin to de-condense back into chromatin. The nuclear envelope re-forms around each set of chromosomes, resulting in two nuclei.
Cytokinesis
While not part of mitosis itself, cytokinesis often occurs simultaneously with telophase. It is the process by which the cytoplasm divides, resulting in two daughter cells, each with a complete set of chromosomes.
Diagram Reference
Unfortunately, I cannot see the specific diagram referenced in "lesson 8 page 2" since I don't have access to the materials you have. However, typically, such a diagram would illustrate the stages of the cell cycle, showing the phases of interphase and mitosis, along with the flow from one phase to the next, possibly with arrows indicating the progression of the cycle. Diagrams often highlight key features, such as the state of the chromosomes during each phase, spindle formation, and cell structures involved in division. If you have further details or a description of the diagram, I could provide more specific insight!