Multiple Choice
Unprocessed mRNA is exported from the nucleus to be processed before translation.
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5. DNA to RNA to Protein
mRNA Export and Nuclear Structures
Multiple Choice
In eukaryotic cells, can RNA leave the nucleus, and if so, which statement best describes how mRNA is exported?
A
Yes; mature mRNA is exported through nuclear pore complexes (NPCs) as an mRNP particle after processing such as capping, splicing, and polyadenylation.
B
No; RNA is permanently retained in the nucleus, and only proteins can cross the nuclear envelope.
C
Yes; mRNA is exported through gap junctions that connect the nucleus directly to the cytosol.
D
Yes; mRNA diffuses freely across the nuclear envelope lipid bilayer without using nuclear pore complexes.
Verified step by step guidance1
Step 1: Understand the structure of the eukaryotic nucleus, which is enclosed by the nuclear envelope, a double lipid bilayer that separates the nucleus from the cytoplasm.
Step 2: Recognize that the nuclear envelope contains specialized channels called nuclear pore complexes (NPCs) that regulate the transport of molecules between the nucleus and cytoplasm.
Step 3: Know that RNA molecules, specifically messenger RNA (mRNA), are synthesized and processed inside the nucleus. Processing includes capping at the 5' end, splicing to remove introns, and polyadenylation at the 3' end.
Step 4: Learn that only mature, fully processed mRNA is exported from the nucleus to the cytoplasm, and this export occurs through the NPCs as part of a ribonucleoprotein complex (mRNP), which protects the mRNA and facilitates its transport.
Step 5: Conclude that mRNA does not diffuse freely across the nuclear envelope nor pass through gap junctions (which connect cytoplasms of adjacent cells, not nucleus to cytosol), and RNA is not permanently retained in the nucleus; instead, mature mRNA exits via NPCs.
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