Alternative exon combination can lead to different proteins

    The primary hnRNA transcript includes both exon- & intron-equvialent sequences. The exon-equivalents (numbered) may correspond to functional regions of the protein, for example, DNA-binding regions or dehydrogenase activity. By removing one or more exon-equivalent regions along with the intron-equivalents, different proteins with different functions can be produced.

    Alternative splicing may explain why genomes can get along with far fewer protein-coding regions than expected.

Figure © 2012 TA Brown, Introduction to Genetics (1st ed.); additional text © 2014 by Steven M. Carr