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Questions and Answers
What are the key stages of mitosis and meiosis?
What are the key stages of mitosis and meiosis?
Prophase, Metaphase, Anaphase, Telophase
What happens during cytokinesis?
What happens during cytokinesis?
Mitosis ensures each daughter cell receives a haploid complement of chromosomes.
Mitosis ensures each daughter cell receives a haploid complement of chromosomes.
False
What is interphase?
What is interphase?
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The cell cycle is described in the sequence: G1 → S → G2 → _____
The cell cycle is described in the sequence: G1 → S → G2 → _____
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What are cyclins?
What are cyclins?
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Which checkpoint is considered the most important?
Which checkpoint is considered the most important?
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The p53 protein acts as a tumor suppressor.
The p53 protein acts as a tumor suppressor.
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What can lead to cancer in relation to the cell cycle?
What can lead to cancer in relation to the cell cycle?
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How long does mitosis typically take?
How long does mitosis typically take?
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Study Notes
Mitosis and Meiosis Overview
- Mitosis is nuclear division, ensuring each daughter cell has a diploid complement of chromosomes identical to the parent cell.
- Cytokinesis follows mitosis, dividing the cytoplasm into two daughter cells.
Key Stages of Mitosis
- Chromosome Duplication: Occurs before nuclear division; DNA replication leads to chromosome duplication.
- Chromosome Separation: Each chromosome divides longitudinally into two identical halves, moving to opposite poles before reaching daughter nuclei.
- Interphase: Non-mitotic cells are in this stage; chromosomes aren’t visible, consisting of G1, S (DNA synthesis), and G2 phases.
Cell Cycle
- The cell cycle includes G1 → S → G2 → M phases; G1 and G2 are intermission phases without DNA replication.
- Cyclins regulate the cell cycle and activate cyclin-dependent kinases; they degrade after fulfilling their function.
- Important checkpoints exist at G1/S and G2/M transitions to ensure proper cell growth and DNA integrity.
Regulation of Cell Cycle
- Checkpoints are crucial for preventing uncontrolled cell division; transition from G1 to S requires adequate cell size and timing since the previous mitosis.
- G2/M checkpoint confirms completion of DNA replication and repair.
- Abnormalities, such as defective p53 (a tumor suppressor), contribute to cancer, allowing rapid cell division.
Role of p53 Gene
- TP53 gene codes for p53 protein, which prevents uncontrolled cell growth.
- p53 acts as a guardian of the genome, inhibiting the cell cycle when abnormalities are detected.
Spindle Assembly Checkpoint (SAC)
- The most critical checkpoint occurs in metaphase, ensuring proper alignment of chromosomes before proceeding with mitosis.
Duration of Cell Cycle
- Cell cycle duration varies by cell type, typically taking 18 to 24 hours; mitosis is relatively short, lasting 0.5 to 2 hours.
Stages of Mitosis Detailed
- Prophase: Chromosomes condense and become visible; the nuclear envelope breaks down, and nucleoli disappear.
- Metaphase: Chromosomes align at the equatorial plane of the cell, preparing for separation.
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