In genetics, the introns are the non-coding nucleotide sequences. RNA splicing removes the introns during splicing. And introns act as both spacers between and stuffers within genes, splicing genes into modules.

A Harvard geneticist by the name of Walter Gilbert named both introns, and their counterpart exons. The human introns are usually enormous and consist of several thousand DNA bases. For this reason, it is hard to clone a gene. That is because the intron-containing gene is, on average, too long to fit into a bacterial plasmid.

Furthermore, introns do not encode RNA or protein. Instead, they exist for various forms of gene regulation. And/or for reasons yet not fully understood.