The structure responsible for moving chromosomes during mitosis is the mitotic spindle , a dynamic, microtubule-based apparatus. The mitotic spindle is primarily composed of microtubules and associated proteins, including motor proteins, which work together to capture, align, and segregate chromosomes into daughter cells. Key components and functions:
- Microtubules form the spindle fibers that emanate from centrosomes (or spindle poles). These fibers attach to chromosomes at specialized sites called kinetochores , located on the centromeres of chromosomes
- Centrosomes serve as microtubule organizing centers that nucleate and anchor spindle microtubules, helping to establish the bipolar spindle structure necessary for chromosome movement
- Motor proteins such as kinesins and dyneins generate forces along microtubules, facilitating chromosome movement toward spindle poles during anaphase and helping to maintain spindle dynamics
- During prometaphase , microtubules attach to kinetochores and chromosomes begin their alignment at the spindle equator (metaphase plate). In anaphase , sister chromatids are pulled apart as kinetochore microtubules shorten, moving chromatids toward opposite poles
- The spindle apparatus ensures accurate chromosome segregation, preventing errors in chromosome number in daughter cells
In summary, the mitotic spindle , composed mainly of microtubules, centrosomes, and motor proteins, is the cellular structure responsible for moving chromosomes during mitosis by capturing them at kinetochores, aligning them, and pulling sister chromatids apart to opposite poles of the dividing cell
