what is the functional and evolutionary importance of introns?
some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during RNA splicing--such variations are called alternative RNA splicing. Because of alternative splicing, the number of different proteins an organism can produce is much greater than its number of genes.
Proteins often have a modular architechture consisting of discrete regions called domains. In many cases, different exons code for the different domains of a protein. Exon shuffling may result in the evolution of new proteins