Final answer:
Processing proteins 'hop off' the polymerase and bind to pre-mRNA to protect it from degradation and assist with translation initiation. The modifications carried out include adding a 5' cap and a poly-A tail, and these changes ensure the mRNA's stability and proper export to the cytoplasm.
Step-by-step explanation:
The process of processing proteins 'hopping' off polymerase tail and binding to pre-mRNA as it emerges involves several critical modifications to the primary transcript or pre-mRNA.
These modifications include the addition of a 5' cap and a poly-A tail, as well as the removal of non-coding sequences (introns). The 5' cap, which is a 7-methylguanosine nucleotide, is added to the 5' end of the growing transcript to protect it from degradation and to assist with the initiation of translation by ribosomes.
The poly-A tail, consisting of about 200 adenine nucleotides, is added at the 3' end after transcription is complete. This tail provides additional protection from degradation and facilitates the export of the mRNA to the cytoplasm. The RNA-stabilizing proteins bind to the pre-mRNA to protect it during these modifications and to ensure its proper processing and transport.