In a eukaryotic cell, which statement best explains why genomic DNA generally cannot leave the nucleus to be translated in the cytoplasm?

• A. DNA cannot leave the nucleus because it is hydrophobic and therefore cannot pass through the aqueous channel of the nuclear pore complex.
• B. It is packaged as large chromatin/chromosome structures that are not transported through nuclear pore complexes; instead, processed mRNA is exported for translation.
• C. DNA lacks introns, so it cannot be recognized by the nuclear export machinery, whereas mRNA contains introns that act as export signals.
• D. DNA is too small to be retained and therefore rapidly diffuses out of nuclear pore complexes unless it is bound to ribosomes.

Answer: (B)

Verified step by step guidance

1. Understand the structure and function of the nuclear envelope and nuclear pore complexes (NPCs), which regulate the transport of molecules between the nucleus and cytoplasm.
2. Recognize that genomic DNA in eukaryotic cells is organized into large chromatin and chromosome structures, making it physically large and complex.
3. Recall that nuclear pore complexes allow selective transport, typically permitting small molecules and certain macromolecules like RNA and proteins to pass, but not large DNA molecules.
4. Know that instead of DNA leaving the nucleus, the cell transcribes DNA into messenger RNA (mRNA), which is processed and exported through the nuclear pores to the cytoplasm for translation.
5. Conclude that the main reason genomic DNA does not leave the nucleus is due to its large, packaged structure and the selective transport mechanism of nuclear pores, not because of hydrophobicity, intron presence, or size alone.