Eukaryotic cells: select the statement that is NOT true of eukaryotes as a group

Introduction / Context:
Distinguishing features of eukaryotic cells include membrane-bound organelles and chromatin architecture. Test questions often probe knowledge of exceptions and organelle-specific traits.

Given Data / Assumptions:

• Eukaryotes possess a true nucleus with a double membrane.
• Eukaryotic chromatin includes histone proteins.
• Mitochondria and chloroplasts are of bacterial ancestry (endosymbiosis) and retain 70S ribosomes.
• Gas vacuoles are typical of some aquatic prokaryotes (e.g., cyanobacteria), not eukaryotes.

Concept / Approach:
We identify the one statement that does not generally describe eukaryotes. Organellar ribosomes (70S) are a classic endosymbiotic hallmark within otherwise 80S cytosolic contexts. Gas vacuoles, used for buoyancy control, are a prokaryotic adaptation and rare to absent in eukaryotes.

Step-by-Step Solution:

Verification / Alternative check:
Review endosymbiotic theory and ribosome sedimentation coefficients: 80S (cytosol) vs 70S (organelles).

Why Other Options Are Wrong:
They correctly describe standard eukaryotic traits and organelle specifics, so they are not the “not true” choice.

Common Pitfalls:
Confusing organelle ribosomes (70S) with cytosolic ribosomes (80S); overlooking prokaryotic adaptations like gas vacuoles.

Final Answer:
Gas vacuoles are present