Question

Spindle fibers are made of
A. Actin protein and RNA
B. Cellulose and RNA
C. Tubulin protein and RNA
D. Both (A) and (C)

Answer 1

Hint:- For an organism to grow, to repair the damaged cells, or to reproduce it has to undergo a process called cell division. Cell division is a part of the cell cycle, at the end of which two or more daughter cells are formed. This division can be mitotic or meiotic. Daughter cells after mitotic cell division have genetic material that is identical to that of the parent cell. Daughter cells formed are genetically different from the parent after they undergo meiotic cell division.

Complete Answer:-Spindle fibers are proteins that are active mainly during the metaphase of cell division. All the daughter cells receive an equal amount of genetic material. Spindle fibers align the chromosomes in such a way that it makes this division of genetic material possible. The spindle fiber emerges out from the centrosome present in the parent cell. During cell division, the centrosomes move towards the poles of the cell, and the spindle fibers that are formed bind to the centromeres of the chromosomes. These chromosomes are now situated in the middle of the parent cell at an equal distance from the centrosomes at the poles.
Microtubules and accessory proteins make up the spindle fibers. Alpha and beta subunits make up microtubules. Once the centrosome receives a cell signal it adds these subunits to increase the length of the microtubules. Spindle fibers have a small amount of RNA as well. While actin proteins do take part in cell division, they do not form spindle fibers. They help transport cell organelles to the daughter cells during mitosis.

The correct answer is Option (C) - Tubulin protein and RNA.


Note:- Spindle fibers formed during mitotic division are called mitotic spindle and during meiotic division, they are referred to as a meiotic spindle. During anaphase which is the next phase in cell division, the spindle fibers pull the identical daughter chromosomes to the opposite ends of the poles. Microtubules also help increase cell size during this phase.