during cell division how do chromosomes move to opposite poles of the cell
During cell division, chromosomes move to opposite poles of the cell through a process called spindle formation and microtubule dynamics. Here is a step-by-step explanation of how chromosome separation occurs:
1. The cell enters a stage called prophase of mitosis, or the first stage of meiosis. During this stage, the chromosomes condense and become visible under a microscope. The nuclear envelope also breaks down.
2. The cell forms a structure called the spindle apparatus. This structure consists of two centrosomes, each containing a pair of centrioles, which move to opposite ends of the cell. Microtubules, long filamentous protein structures, radiate from the centrosomes.
3. The microtubules from one centrosome attach to the kinetochore region of the chromosomes. Kinetochore is a protein structure that forms on the centromere region of each condensed chromosome.
4. Each chromosome is made up of two identical sister chromatids, held together by a region called the centromere. The microtubules attached to the chromosomes exert forces on the kinetochore, causing tension.
5. The tension exerted by the microtubules causes the centromere to split, separating the sister chromatids. Each sister chromatid now becomes an individual chromosome.
6. The microtubules continue to shorten, pulling the chromosomes towards the opposite poles of the cell. This movement is aided by a motor protein called dynein, which slides along the microtubules towards the centrosomes.
7. As the microtubules shorten, non-kinetochore microtubules from one centrosome interact with microtubules originating from the other centrosome. These interactions further push the poles apart, aiding in chromosome separation.
8. At the end of cell division, each pole contains a complete set of chromosomes. The cell then undergoes cytokinesis, dividing into two daughter cells, each with a complete set of chromosomes.
Overall, the coordinated action of microtubules, kinetochores, and motor proteins helps in the accurate separation of chromosomes during cell division.