What is the main function of the spindle fibers during mitosis?

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Question

What is the main function of the spindle fibers during mitosis?

Accepted Answer

Correct Answer: B — To separate the chromosomesStep-by-step Solution:Spindle fibers are dynamic microtubule structures that form the mitotic spindle during cell division. They are composed of tubulin protein polymers. During prometaphase, spindle fibers (specifically kinetochore microtubules) attach to the kinetochores — protein complexes located at the centromere region of each chromosome. During metaphase, spindle fibers align chromosomes at the cell's equatorial plate (metaphase plate). During anaphase, the spindle fibers shorten by depolymerization, pulling the sister chromatids apart toward opposite poles of the cell. This ensures that each daughter cell receives an identical set of chromosomes. This is the primary and most critical function of spindle fibers.Why other options are wrong: (A) Cell growth regulation involves growth factors, proto-oncogenes, and tumor suppressor genes — not spindle fibers. (C) DNA synthesis (replication) occurs during the S phase of interphase, involving DNA polymerase — not spindle fibers. (D) DNA repair is carried out by specific enzymes (nucleases, ligases, polymerases) — not spindle fibers.Extended Explanation:The mitotic spindle consists of three types of microtubules: (1) Kinetochore microtubules — attach to chromosomes at kinetochores and pull them apart; (2) Polar microtubules (interpolar) — extend from each pole and overlap in the middle, pushing poles apart; (3) Astral microtubules — radiate outward from the centrosome and help position the spindle in the cell. The centrosome (containing two centrioles in animal cells) organizes the spindle. In plant cells, spindle forms from diffuse MTOCs (microtubule organizing centers) without centrioles. Drugs like colchicine and vinblastine depolymerize spindle fibers and are used as antimitotic agents in cancer chemotherapy.Key Concepts: Mitosis, spindle apparatus, chromosome segregation, anaphase, kinetochore, microtubules.

What is the main function of the spindle fibers during mitosis?

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What is the main function of the spindle fibers during mitosis?

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