Which nuclear structure cannot be clearly visualized with standard electron microscopy due to insufficient density?

Which nuclear structure cannot be clearly visualized with standard electron microscopy due to insufficient density?

• A. Nucleolus.
• B. Chromatin.
• C. Nuclear lamina and pores.
• D. Ribosomes.

Answer: (C)

Electron microscopy relies on contrast from electron-dense material to reveal structures. Structures rich in nucleic acids and ribonucleoproteins, like the nucleolus, chromatin, and ribosomes, bind heavy-metal stains well and stand out clearly. The nuclear lamina and nuclear pore complexes, on the other hand, are protein-based and relatively low in intrinsic density, forming a delicate mesh beneath the inner nuclear membrane and spanning the envelope. Because their density is modest, standard electron microscopy doesn’t provide strong contrast for them, so they’re not clearly visualized without additional techniques that enhance contrast or resolution.

Electron microscopy relies on contrast from electron-dense material to reveal structures. Structures rich in nucleic acids and ribonucleoproteins, like the nucleolus, chromatin, and ribosomes, bind heavy-metal stains well and stand out clearly. The nuclear lamina and nuclear pore complexes, on the other hand, are protein-based and relatively low in intrinsic density, forming a delicate mesh beneath the inner nuclear membrane and spanning the envelope. Because their density is modest, standard electron microscopy doesn’t provide strong contrast for them, so they’re not clearly visualized without additional techniques that enhance contrast or resolution.