The Genome of a cell or organism is the same as that of the entire organism. However, the proteome of an organism is much greater than that of each cell (unless the organism is unicellular). How do you account for the presence of more variation among of proteins than there are in genes?
The simple answer would be "there are more proteins than genes", but I'm more interested in why. Is it sufficient to say that during gene expression a single gene codes for multiple proteins (Alternative Splicing) and ribosomes translating mRNA to polypeptide chains (Posttranslational modification)? Could someone expand more on this?