The nuclear pore complex in eukaryotic cells allows bidirectional transport of macromolecules between the nucleus and cytoplasm. Which molecules are exported from the nucleus to the cytoplasm?
Answer and explanation
Correct answer: C. Ribosomal subunits, mRNA, and tRNA
- Step 1: Nuclear pore complexes act as selective aqueous gates traversing the double-membrane nuclear envelope.
- Step 2: Soluble proteins required for nuclear functions (e.g., DNA and RNA polymerases, histones, transcription factors) are synthesized in the cytoplasm and imported through the pore.
- Step 3: Processed RNA species (mRNA, tRNA) and assembled ribonucleoprotein complexes (ribosomal subunits) are specifically recognized by exportins and exported to the cytoplasm for translation.
Answer
Ribosomal subunits, mRNA, and tRNA.
Why not the others: DNA polymerase and RNA polymerase are synthesized in the cytoplasm and imported into the nucleus; Histone proteins are translated in the cytoplasm and imported into the nucleus to assemble chromatin; Intact chromosomes are retained within the nuclear boundary.
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