Which statement describes RNA processing in eukaryotes?

Which statement describes RNA processing in eukaryotes?

• A. A primary transcript is capped, spliced, and polyadenylated before translation.
• B. Transcripts are never capped or polyadenylated.
• C. Only introns are removed; exons are joined with no modification.
• D. Transcripts are translated directly without processing.

Answer: (A)

RNA processing in eukaryotes converts the initial transcript into a mature messenger RNA by adding a 5' cap, removing introns through splicing, and adding a 3' poly-A tail. The 5' cap protects the transcript and helps ribosomes start translation; splicing removes noncoding introns and joins the coding exons; the poly-A tail stabilizes the mRNA, aids export from the nucleus, and enhances translation efficiency. These processing steps happen before the mRNA is exported to the cytoplasm and translated. Transcripts are indeed capped and polyadenylated, and translation uses the mature mRNA rather than the unprocessed primary transcript, so both of the other statements misstate the process.

RNA processing in eukaryotes converts the initial transcript into a mature messenger RNA by adding a 5' cap, removing introns through splicing, and adding a 3' poly-A tail. The 5' cap protects the transcript and helps ribosomes start translation; splicing removes noncoding introns and joins the coding exons; the poly-A tail stabilizes the mRNA, aids export from the nucleus, and enhances translation efficiency. These processing steps happen before the mRNA is exported to the cytoplasm and translated. Transcripts are indeed capped and polyadenylated, and translation uses the mature mRNA rather than the unprocessed primary transcript, so both of the other statements misstate the process.