Which modification is added to the 3' end of mRNA during processing?

• A. A 5' cap.
• B. A poly(C) tail.
• C. Spliceosome complex.
• D. A poly(A) tail.

Answer: (D)

In eukaryotic mRNA processing, the modification added to the 3' end is a poly(A) tail. This tail, made of many adenine nucleotides, helps stabilize the mRNA, aids its export from the nucleus, and enhances translation by interacting with poly(A)-binding proteins. By contrast, the 5' end receives a cap early in processing, which protects the transcript and assists ribosome recognition, and splicing removes introns via the spliceosome. A poly(C) tail isn’t a feature of standard mRNA processing.