Final answer:
Before RNA can be packaged, it undergoes several post-transcriptional modifications including the stabilization with proteins, the addition of a 5' cap, the removal of introns, the splicing of exons, and the addition of a poly-A tail to protect the molecule and signal cellular machinery for its translation into protein.
Step-by-step explanation:
Post-Transcriptional Modifications of RNA
Before RNA is packaged and translated into proteins, it must undergo several post-transcriptional modifications. RNA polymerase II transcribes long precursor RNAs, known as pre-mRNA, which must be processed into mature mRNAs. This processing includes the addition of RNA-stabilizing proteins that protect the pre-mRNA from degradation, as well as several critical steps:
- Addition of a 5' cap to the 5' end of the transcript, which helps in preventing degradation and is recognized by protein synthesis factors to initiate translation.
- Excision of introns, which are non-coding sequences, and splicing of exons, which are the coding sequences that specify the appropriate amino acids for the protein.
- Addition of a poly-A tail at the 3' end, which further protects the mRNA from degradation and signals that the transcript needs to be exported to the cytoplasm.
These steps are essential to produce a functional messenger RNA molecule that can be translated into a protein. Without these post-transcriptional modifications, the RNA would not be correctly processed, would likely be degraded, and no protein would be synthesized as a result.