Which chemical group is added to the 5' end of mRNA during RNA processing?

During RNA processing, a methyl-G cap is added to the 5' end of the mRNA. This chemical modification is crucial because it serves several important functions. The methyl-G cap protects the mRNA from degradation by exonucleases, which are enzymes that break down RNA. It also plays a significant role in the initiation of translation, as it helps ribosomes recognize and bind to the mRNA to start protein synthesis. Additionally, the cap assists in the export of mRNA from the nucleus to the cytoplasm, ensuring that the messenger RNA is properly processed and functional for translation.

In contrast, while a Poly A-tail, added to the 3' end of mRNA, helps stabilize the mRNA and aids in its export from the nucleus, it does not occur at the 5' end. Nitrogen bases and phosphate groups are integral components of nucleotides making up RNA, but they are not specific modifications made during the processing of mRNA. The addition of the methyl-G cap is a distinct and essential step that directly influences the stability and functionality of mRNA.