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