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Which organisms are the exceptions to the 9 + 2 microtubule arrangement in cilia and flagella?
publish date: 2026/06/15 21:36:51.944057 UTC
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The 9 + 2 arrangement is characteristic of virtually all cellular cilia and flagella - but two groups of organisms are exceptions.
Which organisms are these exceptions?
Correct Answer
Bacteria and blue-green algae
Explanation
Bacteria and blue-green algae (cyanobacteria) are the exceptions to the 9 + 2 arrangement. Their flagella have a fundamentally different structure - they are rotating protein filaments powered by a molecular motor, rather than the sliding microtubule system found in eukaryotic cilia and flagella.
Reference
Biology: A Self-Teaching Guide