introns

Introns are segments of genetic material found within genes that do not code for proteins. When a gene is used to make a protein, the entire gene is transcribed into a preliminary messenger RNA (mRNA). Before this mRNA can be used to produce a protein, the introns are cut out and the remaining coding regions, called exons, are joined together. This process, called splicing, ensures that the final mRNA contains only instructions for building the protein. Introns are thought to play roles in gene regulation and evolution, although they do not directly code for proteins.