Final answer:
mRNA splicing in eukaryotes involves the removal of introns by spliceosomes, and is tightly linked to mRNA export to the cytoplasm. Alternative splicing can create multiple protein variants from a single gene, and a poly-A tail and 5' cap on mRNA are other key modifications aiding in its stability and export.
Step-by-step explanation:
Eukaryotic mRNA splicing is a process that involves the precise removal of introns from a primary RNA transcript to create mature RNA ready for translation. Spliceosomes, protein-RNA complexes, catalyze the splicing process by recognizing the intron-exon boundaries and facilitating the excision of introns. Concurrently, splicing is coupled to mRNA export from the nucleus, as the processing of mRNA, including splicing and addition of a poly-A tail, signals it as mature and ready for export to the cytoplasm where translation occurs.
Alterations in the splicing mechanism can lead to alternative splicing, which allows a single gene to produce multiple protein variants. This diversity in mRNA molecules is crucial for cellular function and allows for a greater complexity of protein expression from a limited number of genes. Export of mRNA involves additional signals such as a 5' cap and a 3' poly-A tail which ensure the mRNA's stability and facilitate its movement from the nucleus to the cytoplasm. These coupled processes of splicing and export are essential for proper gene expression in eukaryotic cells.