What key processing steps convert a primary transcript into mature eukaryotic mRNA?

What key processing steps convert a primary transcript into mature eukaryotic mRNA?

• A. 5' capping, 3' polyadenylation, and splicing to remove introns and join exons.
• B. 5' polyadenylation, 3' capping, and translation.
• C. Splicing only; capping occurs after translation.
• D. 3' capping, 5' polyadenylation, and translation.

Answer: (A)

After transcription, a eukaryotic pre-mRNA must be converted into mature mRNA through specific processing steps that prepare it for export from the nucleus and for translation in the cytoplasm. The 5' end is capped soon after transcription begins, protecting the RNA and helping ribosomes recognize the message. At the 3' end, a poly(A) tail is added, which increases stability and facilitates export and translation. In addition, introns are removed and exons stitched together in a process called splicing, producing a continuous, translatable coding sequence. All three modifications work together to produce a stable, exportable, translatable mRNA molecule. Translation is not a maturation step; it occurs after the mRNA has been processed and exported. Splicing alone would leave ends uncapped and unglycosylated, and capping or polyadenylation without the others would not produce a fully functional mRNA.

After transcription, a eukaryotic pre-mRNA must be converted into mature mRNA through specific processing steps that prepare it for export from the nucleus and for translation in the cytoplasm. The 5' end is capped soon after transcription begins, protecting the RNA and helping ribosomes recognize the message. At the 3' end, a poly(A) tail is added, which increases stability and facilitates export and translation. In addition, introns are removed and exons stitched together in a process called splicing, producing a continuous, translatable coding sequence. All three modifications work together to produce a stable, exportable, translatable mRNA molecule.

Translation is not a maturation step; it occurs after the mRNA has been processed and exported. Splicing alone would leave ends uncapped and unglycosylated, and capping or polyadenylation without the others would not produce a fully functional mRNA.