Chromosome composition: Which component is NOT a structural part of a human chromosome at any phase of the cell cycle?

Introduction / Context:
Human chromosomes are DNA-protein complexes with characteristic structural units. Distinguishing true chromosomal components from organelles that participate in cell division prevents conceptual errors in cell biology.

Given Data / Assumptions:

• Considering canonical chromosome architecture across interphase and mitosis.
• Evaluating core chromatin elements versus cytoplasmic structures.

Concept / Approach:
Nucleosomes are the fundamental chromatin units formed by DNA wrapped around histone octamers; histones are core proteins of chromatin. Centromeres and telomeres are specialized chromosomal regions essential for segregation and stability. Centrioles, by contrast, are microtubule-based organelles of the centrosome that help organize the spindle; they are not part of the chromosome itself.

Step-by-Step Solution:

Verification / Alternative check:
Textbook diagrams place centrioles at spindle poles; chromosomes attach via kinetochores at centromeres, highlighting distinct roles.

Why Other Options Are Wrong:

• Histone and nucleosome: core chromatin components.
• Centromere and telomere: specialized chromosomal regions fundamental to function.

Common Pitfalls:
Confusing spindle apparatus components with chromosomal elements due to their close functional association during mitosis.

Final Answer:
Centriole