After an RNA molecule is transcribed from a eukaryotic gene, Introns are removed and Exons are spliced together to produce an mRNA molecule with a continuous coding sequence.
In most eukaryotic genes, coding regions (exons) are interrupted by noncoding regions (introns). During transcription, the entire gene is copied into a pre-mRNA, which includes exons and introns. However, during the process of RNA splicing, introns are removed and exons joined to form a contiguous coding sequence.