Difficulty: Easy
Correct Answer: Spindle (mitotic spindle)
Explanation:
Introduction / Context:Cell division requires precise segregation of genetic material. A specialized, microtubule-based structure organizes and drives chromosome movement. Knowing the names and roles of related structures helps distinguish the components of mitosis and meiosis.
Given Data / Assumptions:
Concept / Approach:The mitotic spindle is composed of microtubules and associated motor proteins. It arises from centrosomes (in many animal cells) and attaches to chromosomes via kinetochores. By polymerization/depolymerization and motor activity, it positions and separates sister chromatids to daughter cells.
Step-by-Step Solution:
Identify “network of protein cables” → microtubule arrays.Name of the whole apparatus that moves chromosomes → spindle.Differentiate spindle from accessory structures (aster, kinetochore).Choose “Spindle (mitotic spindle).”Verification / Alternative check:Fluorescent microscopy during mitosis shows bipolar spindle fibers attaching to kinetochores and pulling chromatids apart at anaphase.
Why Other Options Are Wrong:
Aster: Star-shaped microtubules radiating from centrosomes; not the full network coordinating segregation.Kinetochore: Protein complex on centromeres; a docking site for spindle microtubules, not the entire network.Chromatid: One of the duplicated DNA molecules; not a microtubule structure.Centrosome: Microtubule-organizing center; not the cable network itself.Common Pitfalls:Equating any mitotic structure with the spindle. The spindle is the complete bipolar microtubule array plus motors; asters and kinetochores are parts within this system.
Final Answer:Spindle (mitotic spindle).
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