Before an mRNA leaves the nucleus, it receives two protective modifications at its two ends. What are these two modifications called?
AA 5' UTR and a 3' UTR
BA TATA box and a CpG island
CAn intron and an exon
DA 5' cap and a poly-A tail
Answer & Solution
Correct answer: D. A 5' cap and a poly-A tail
1. Before mRNA leaves the nucleus, it is given two protective modifications that prevent the ends of the strand from degrading.
2. The 5' cap is placed on the 5' end and is usually a methylated guanosine triphosphate molecule.
3. The poly-A tail is attached to the 3' end and is usually a series of adenine nucleotides.
4. UTRs are untranslated regions rather than end-cap modifications, and the TATA box and CpG island belong to the promoter and epigenetic systems, not RNA end protection.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 16 "Gene Expression", section Control of RNA Stability_
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