What moves the chromatids during mitosis?
The correct answer and explanation is :
The structure that moves the chromatids during mitosis is the mitotic spindle. The mitotic spindle is a network of protein fibers that is responsible for organizing and segregating the chromosomes during mitosis. It is made up of microtubules, which are dynamic structures that grow and shrink in length to facilitate chromosome movement.
Explanation:
During mitosis, the cell undergoes a series of phases: prophase, metaphase, anaphase, and telophase. Each phase plays a crucial role in ensuring the accurate division of the cell’s genetic material, which is crucial for the formation of two genetically identical daughter cells. The process of moving chromatids occurs primarily during anaphase.
- Formation of the Mitotic Spindle:
In the early stages of mitosis, during prophase, microtubules begin to form the mitotic spindle. The spindle fibers emanate from structures called centrosomes, which are located near the poles of the cell. These microtubules connect to the kinetochores of the chromosomes (specific protein complexes attached to the centromeres of the chromosomes). This connection is essential for the movement of the chromatids. - Chromatid Movement:
During metaphase, the chromosomes align along the cell’s equator, known as the metaphase plate, with each sister chromatid attached to opposite spindle poles. At this stage, the tension exerted by the spindle fibers ensures the chromatids are in perfect alignment. In anaphase, the centromere that holds the sister chromatids together splits. The spindle fibers then shorten, and the microtubules attached to the kinetochores pull the chromatids toward opposite poles of the cell. The dynamic behavior of microtubules—growing and shrinking—pushes and pulls the chromatids efficiently. This movement is facilitated by motor proteins, such as dynein and kinesin, which help to either move the chromosomes along the microtubules or help regulate their dynamics. - Telophase and Cytokinesis:
Finally, in telophase, the chromatids reach the poles, and the nuclear membrane reforms around each set of chromosomes. Cytokinesis then follows, dividing the cytoplasm into two, completing the cell division process.
In summary, the mitotic spindle, composed of microtubules and regulated by motor proteins, is the key structure responsible for moving chromatids during mitosis, ensuring the precise separation of genetic material between daughter cells.