Alternative splicing leads to different proteins

The primary RNA transcript includes both exon- & intron-equvialent sequences. The exon-equivalents (numbered) frequently correspond to functional regions of the protein. 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 fewer coding regions than expected.

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