Main protein of mitotic spindle is:

Question

Accepted Answer

The correct option is 2:

The mitotic spindle is a crucial cellular structure responsible for segregating chromosomes accurately into daughter cells during mitosis. It is primarily composed of long fibers called microtubules. These microtubules are polymers of a globular protein known as tubulin. During cell division, tubulin monomers polymerize to form these microtubules, which then assemble to create the spindle apparatus. Different types of microtubules, all made of tubulin, play distinct roles in the mitotic spindle, such as kinetochore microtubules attaching to chromosomes, polar microtubules extending from spindle poles, and astral microtubules radiating from the poles. Therefore, tubulin is undeniably the main protein building block of the mitotic spindle, essential for its formation and function.

The incorrect option is 1: Dynein. Dynein is a motor protein that moves along microtubules, but it is not the main structural protein of the mitotic spindle itself. While dynein plays a role in spindle assembly and chromosome movement by interacting with microtubules, it acts as a motor rather than a primary building block.

The incorrect option is 3: Myosin. Myosin is a motor protein primarily associated with actin filaments, playing a key role in muscle contraction and various cell movements, but it is not a component of the microtubule-based mitotic spindle.

The incorrect option is 4: Tropomyosin. Tropomyosin is a protein associated with actin filaments in muscle and non-muscle cells, involved in regulating actin-myosin interactions. It has no direct structural role in the formation or function of the mitotic spindle.