Number of genes and number of proteins in humans - (Apr/07/2009 )

Could someone please explain to me why humans have 30,000-40,000 genes but more than 50,000 proteins. I thought eukaryotic mRNA was monocistronic. I remember learning the answer a while back but I can't remember.

Does it have something to do with the cleaving of certain exons during RNA splicing creating different variations of a protein that are similar but not the same?

Alternative-splicing is your answer.