During mitosis, what cellular structure is primarily responsible for moving chromosomes toward opposite poles of the cell?

• A. Ribosomes that generate force by synthesizing proteins on the surface of chromosomes
• B. Intermediate filaments that form the nuclear lamina and push chromosomes toward the poles
• C. Spindle microtubules (kinetochore microtubules) that attach to kinetochores and shorten to pull sister chromatids apart
• D. Actin filaments in the contractile ring that constrict the cell membrane during cytokinesis

Answer: (C)

Verified step by step guidance

1. Identify the phase of the cell cycle involved: The question refers to mitosis, the process where duplicated chromosomes are separated into two daughter cells.
2. Recall the main cellular structures involved in chromosome movement during mitosis: These include microtubules (specifically spindle microtubules), intermediate filaments, actin filaments, and ribosomes.
3. Understand the role of spindle microtubules: Spindle microtubules attach to chromosomes at specialized protein complexes called kinetochores and generate force by shortening, pulling sister chromatids toward opposite poles.
4. Eliminate incorrect options by their functions: Ribosomes synthesize proteins but do not generate force to move chromosomes; intermediate filaments provide structural support but do not move chromosomes; actin filaments form the contractile ring during cytokinesis, which occurs after chromosome separation.
5. Conclude that spindle microtubules (kinetochore microtubules) are the primary structures responsible for moving chromosomes toward opposite poles during mitosis.