Question

Mitotic spindle is mainly composed of _________ protein.
(a) Tubulin
(b) Myosin
(c) Actin
(d) Actomyosin

Answer 1

Hint: Spindle fibres are composed of a large number of microtubules. It is made up of a single layer of globulin protein.

Complete answer:
Spindle fibres consist of microtubules that are polymeric chains synthesized from the protein Tubulin.
Additional information:
- The spindle apparatus or spindle fibres denotes the cytoplasmic structure of eukaryotic cells that forms during cellular division to separate sister chromosomes between daughter cells.
- It is referred to as the mitotic spindle during mitosis, a process which forms genetically identical daughter cells, or the meiotic spindle during meiosis, a process during which gametes with half the number of chromosomes of the parent cell are produced.
- Besides chromosomes, the spindle apparatus consists of many proteins.
- Microtubules encompass the most abundant components of the apparatus which are made up of tubulin.
- The centrosomes are small organelles found in the cell that organize and arrange the microtubules that later form the spindle fibres.
- The spindle fibres begin to form during prophase of cell division. They begin to look something like a spider with lots of legs when they start to form.
So, the correct answer is “tubulin”.

Note: The spindle fibres form during cell division near the poles of the dividing cell. As the fibres extend across the cell, they look for the centromere of each chromosome. Once attached to the centromere, the spindle fibre is pulled back. With each fibre comes the chromosomes that are attached to the fibres, which separates the chromosomes along the poles. Once the chromosomes are completely separated and reach the poles, the spindle fibres disappear.