text: An exon is a portion of a gene that goes into the final mRNA transcript. Introns would be the sections of DNA that are non-coding. Think of exons as being the parts that don't get snipped out when it comes time to actually make the real part of RNA that gets translated to a protein.\n\nAny number of proteins could be produced from a gene that has three exons. This is because the code contained within the three exons, comprising the coding portion of the gene, could contain several open reading frames (ORFs) within the portion that is transcribed, depending on the size of the gene and the position of the promoters.