Question

Which of the following protein forms spindle fibres?
(a) Tubulin
(b) Myosin
(c) Actomyosin
(d) Myoglobin

Answer 1

Hint: Spindle fibres are produced from a protein that polymerizes into long chains or filaments to form microtubules, hollow fibres which serve as a skeletal system for living cells. These are cellular structures which are mainly used during cell division.

Complete answer:
-During the process of cell division spindle fibres are formed. These are formed from microtubules which are made up of a protein called tubulin.
- Centrosome is also known as MTOC or Microtubule Organizing Centre. These always have some pre-assembled microtubules.
-Small proteins on the surface of MTOC are responsible for the shortening of microtubules.-During cell division these have additional subunits of alpha-tubulin and beta-tubulin.
-It is present in the cytosol.

Additional information:
-Spindle fibres are microscopic protein structures which help divide genetic material during cell division.
-Spindle fibres start developing during late prophase and are clearly visible in metaphase.
-They are formed from microtubules near the poles of the dividing cell.
-These are attached to the centre of each chromosome. Once attached, the spindle fibre is pulled back. With each fibre comes the chromosomes which separates them along the poles.
-Microtubules act as conveyor belts inside the cells.
-Proteins present on them help move vesicles, granules and other organelles.
-The protein tubulin is itself a globular protein. Microtubules are linear polymers of this globular protein.
-They are also involved in the beating of cilia and flagella.

So the correct answer is Tubulin.

Note: Synthesis of tubulin protein takes place in {G}_{2} phase. Structural support, intracellular support and DNA segregation are provided to eukaryotic cells by tubulin protein.