The presence of introns in RNA plays a crucial role in the process of gene expression, particularly by allowing for alternative RNA splicing. Introns are non-coding sequences that are transcribed into RNA but are not included in the final mature mRNA that is translated into protein. During RNA processing, introns are removed, and exons (the coding sequences) are spliced together.
Alternative splicing is the process by which different combinations of exons are joined together to produce multiple distinct mRNA variants from a single gene. This allows for the generation of diverse protein isoforms from one gene, which can have different functions, locations, or regulation in the cell. Essentially, introns provide the flexibility necessary for cells to create a variety of proteins, enhancing the complexity of an organism's proteome without the need for a corresponding increase in the number of genes. This is a key aspect of eukaryotic gene expression and is crucial for the proper functioning and adaptability of cells.