Final answer:
During eukaryotic mRNA processing, a 5' cap is added, a poly-A tail is appended at the 3' end, and introns are removed by splicing. A ribosome recognition sequence is not added; the 5' cap serves as the ribosome binding site.
Step-by-step explanation:
The student's question asks which of the following does not occur during the processing of eukaryotic mRNA: a 5' guanosine cap is added, several adenine (A) residues are added at the 3' end, introns are removed by splicing, or a ribosome recognition sequence is added. During processing, the following events occur:
- A 5' guanosine cap is added.
- Several adenine (A) residues, also known as a poly-A tail, are added at the 3' end.
- Introns are removed during splicing.
The step that does not occur is the addition of a ribosome recognition sequence. Instead, the 5' cap itself serves as the recognition point for ribosome binding in eukaryotes during the initiation of translation. Therefore, the correct answer is that a ribosome recognition sequence is not added during eukaryotic mRNA processing.