What post-transcriptional modification protects eukaryotic mRNA molecules from enzymatic degradation in the cytoplasm and facilitates ribosome binding?
Answer and explanation
Correct answer: C. Addition of a 5' 7-methylguanosine cap and a 3' poly-A tail
- Step 1: Identify standard pre-mRNA processing steps in eukaryotes.
- Step 2: The addition of a 5' 7-methylguanosine cap protects against 5' exonucleases and assists translation initiation, while the 3' polyadenylation (poly-A tail) prevents 3' degradation and promotes nuclear export.
Answer
Addition of a 5' 7-methylguanosine cap and a 3' poly-A tail.
Why not the others: Exons are spliced together, while introns are removed; histones wrap genomic DNA, not mRNA; RNA ribose is not 2'-phosphorylated.
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