Question

Select the correct option: Mitotic spindle is mainly composed of ____ proteins.
A. Tubulin
B. Myosin
C. Actin
D. Actomyosin

Answer 1

Hint:Mitotic spindle also called spindle apparatus. It is the collection of all the spindle fibers formed during mitosis or meiosis. The spindle fibres move and segregate chromosomes during nuclear division.

Complete answer:
Spindle fibres are the network of filaments. They first appear in prophase. They are made up of microtubules. During mitosis, these filaments form at opposite poles of the cell and meet at equatorial planes. Mitotic spindle also contains microtubules proteins. They are the proteins bound to the microtubules. Now, let us study the options given.

Option A: Tubulin: Tubulin are the major block of microtubules. They are important components of cytoskeleton. They polymerize into long chains or filaments and form microtubules. Mitotic spindle contains spindle fibres, which in turn are made of tubulin. Therefore, this is the correct option.

Option B: Myosin: It belongs to the family of motor proteins. These proteins bind action, hydrolyze ATP and transduce force. It helps in muscle contraction. Therefore, this is the incorrect option.

Option C: Actin: It is an intracellular protein present in eukaryotic cells and helps in muscle contraction and cell movements. Therefore, this is the incorrect option.

Option D: Actomyosin: It is a protein complex made of actin and myosin. It plays a role in muscle contraction and is found in muscle fibres. Therefore, this is the incorrect option.

Hence, the correct answer is option ‘A’.

Note:In metaphase, spindle fibres facilitate the chromosomes to the metaphase plate. In anaphase, the chromatids move apart and towards opposite poles. The function of the mitotic spindle is to pull the duplicated chromosomes apart.