A protein isoform is a version of a protein with only small differences to another isoform of the same protein. [1] Different forms of a protein may be produced from different but related genes, or may arise from the same gene by alternative splicing. A large number of isoforms are caused by single nucleotide polymorphisms, small genetic differences between alleles of the same gene.
The discovery of isoforms explains the apparently small number of coding genes revealed in the human genome project: the ability to create categorically different proteins from the same gene increases the diversity of the proteome. Isoforms are readily described and discovered by microarray studies and cDNA libraries.
