RNA modification must be performed in order to form the various proteins needed for eukaryotes to function. RNA modification generates mature RNA. Through RNA modification, a eukaryotic cell can use fewer variations in base pairs of the genetic code (DNA and RNA) while creating proteins with diverse functions. One of the most common methods employed by eukaryotes is to use spliceosomes to cleave out introns (intervening sequences/ non coding proteins) of the pre-RNA, leaving only exons (expressed sequences/coding proteins). Cutting out the intron segments allows for the possibility of exon to rearrangement. Spicing all exons together is called mature mRNA.
What's the advantage of spitting genes? Exons are segments that coding proteins and give proteins specific functions. This leads to the concept of exon shuffling. Exons shuffling is the rearrangement of the exons in the mRNA. These mRNA will come up with different types of proteins with different functions, binding sites, and catalytic sites. This path could lead to the evolution of new proteins.
Even though the use of exons and introns are quite common in eukaryotes, such practice is rarely performed by prokaryotes. In addition, evolution has shown that DNA sequences of genes encoding proteins were conserved. They showed that introns were once appeared in the prokaryotes' ancestral genes, and were vanished over time. The reason for this might be because such processes are not time efficient. Time efficiency is very important for prokaryotes because they multiply at a very fast rate.