Mechanisms and Positions of microtubules

Abstract

Cytokinesis is the division of the cytoplasm of a cell after the division of the nucleus during cell division. Before cytokinesis, mitosis occurs which is a multi-step process that produces two identical daughter cells during its phases (prophase, prometaphase, metaphase, anaphase, and telophase). In short, during prophase the nucleolus disappears and the centrioles begin to move to opposite ends of the cell and fibers extend from the centromeres. During prometaphase, the nuclear membrane dissolves and microtubules attach at the kinetochores, along with the chromosomes beginning to move. During metaphase, the chromosomes align on the metaphase plate. During anaphase, the chromosomes separate and move to the opposite sides of the cell. The motion is a combination of kinetochore movement and the physical interaction of polar microtubules (uneven distribution of electric charge). Lastly, telophase is when the chromatids arrive at opposite poles of the cell new membranes form around the nuclei. Completing the mitotic cycle is the process of cytokinesis, which results when a fiber ring composed of actin around the middle of the cell pinches the cell into two daughter cells (each with their own nucleus). The spindle fibers that pull the centromeres to opposite ends are called microtubules. These microtubules are stiff, long, and have a cylindrical structure and are composed of tubulin. Generally, these regulate the shape and movement of the cell. During cytokinesis, the microtubules assemble in a certain way and have their own mechanisms. There has also been a new study discussing a microtubule-dependent microtubule generation and digs deep into how microtubules are nucleated and distributed inside the spindle. In particular, the discovery has utilized quantitative image analysis to advance the understanding of the spindle structure of animal cells.