FAQs on Cell Cycle & Cell Division Phases Video Lecture - Biology Class 11 - NEET
1. What is the cell cycle and how is it regulated? |
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Ans. The cell cycle refers to the sequence of events that occur in a cell leading to its division and the production of two daughter cells. It consists of interphase (G1, S, and G2 phases) and mitosis (prophase, metaphase, anaphase, and telophase). The cell cycle is regulated by various checkpoints, such as the G1, G2, and M checkpoints, that ensure the cell is ready to proceed to the next phase. These checkpoints monitor DNA integrity, cell size, and the presence of growth factors.
2. What are the phases of mitosis and what happens during each phase? |
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Ans. Mitosis is a process of cell division that occurs after the interphase. It consists of four phases: prophase, metaphase, anaphase, and telophase. During prophase, the chromatin condenses into chromosomes, the nuclear envelope breaks down, and the mitotic spindle forms. In metaphase, the chromosomes align at the cell's equator. Anaphase is characterized by the separation of sister chromatids, which are pulled towards opposite poles of the cell. Telophase involves the formation of two daughter nuclei, and the cytoplasm starts to divide.
3. What is the significance of the G1 phase in the cell cycle? |
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Ans. The G1 phase is the first phase of interphase, occurring before DNA synthesis (S phase). It is a critical phase as it determines whether the cell will proceed to divide or enter a non-dividing state called the G0 phase. During the G1 phase, the cell grows, synthesizes proteins, and replicates its organelles. It also undergoes a series of checkpoints that assess DNA damage, cell size, and nutrient availability. If these checkpoints are not passed, the cell may undergo apoptosis or enter the quiescent G0 phase.
4. How does cell division contribute to growth and repair in multicellular organisms? |
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Ans. Cell division is crucial for growth and repair in multicellular organisms. Through cell division, a single cell can give rise to two daughter cells, leading to an increase in the total number of cells in the organism. During growth, cell division allows for the development and enlargement of tissues and organs. In the case of repair, damaged or injured tissues can be regenerated through cell division. For example, when a cut occurs, nearby cells divide and fill the gap, facilitating the healing process.
5. What are the consequences of uncontrolled cell division? |
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Ans. Uncontrolled cell division can lead to the formation of tumors and cancer. When the normal regulatory mechanisms of the cell cycle fail, cells can divide excessively and form a mass of abnormal cells called a tumor. If the tumor is benign, it remains localized and does not spread to other parts of the body. However, if the tumor becomes malignant, it can invade nearby tissues and metastasize to distant sites, causing cancer. Understanding the regulation of cell division is crucial in preventing and treating cancer.