Isoform described in the chemical composition a molecule of identical, but different structure as compared with a second.
In molecular biology, however, one speaks of an isoform, if a version of a gene, an RNA or a protein with slight to major differences occurs. Splice variants are often the cause of RNA or protein isoforms, i.e., a gene is expressed in various variants. Other post-transcriptional (see transcription (biology ), eg RNA Edition) or post-translational modifications (see Translation ( biology), eg glycosylation ) can cause different isoforms. Also related genes and pseudogenes, probably by gene duplication from a common ancestral gene, are sometimes referred to as isoforms.
The discovery of many isoforms explains the relatively small number of genes has been found in the human genome project: the ability to produce many different gene enhances the diversity of the genome by a multiple.
Genetic isoforms can be assayed by RT-PCR, screening of cDNA libraries, Western blots, and many other techniques of molecular biology.