Intron

An intron is a segment of DNA within a gene that does not code for protein. During the process of gene expression, DNA is transcribed into RNA, but introns are typically removed before the final messenger RNA (mRNA) is used to make a protein. Think of introns as non-essential "filler" or non-coding sections that are cut out, allowing the remaining parts, called exons, to be joined together to form the instructions for building a protein. While once considered "junk," ongoing research shows introns may have regulatory or other functional roles in the genome.