RNA processing yields mature mRNA by which processes?

• A. RNA processing includes the excision of introns, splicing of exons, and addition of a 5' cap and poly(A) tail.
• B. RNA processing only includes translation.
• C. RNA processing only takes place in mitochondria.
• D. RNA processing converts RNA to DNA.

Answer: (A)

RNA processing converts a nascent transcript into mature mRNA through several coordinated modifications. The 5' end is capped, protecting the RNA and helping ribosomes recognize the message. Introns are removed and exons are spliced together to create a continuous coding sequence. The 3' end receives a poly(A) tail, which increases RNA stability, aids export from the nucleus, and enhances translation efficiency. Translation happens after processing, in the cytoplasm, so it is not part of RNA processing. While mitochondria have their own RNA systems, nuclear-encoded mRNA processing is not restricted to mitochondria, and converting RNA to DNA is not part of RNA processing.