What are the roles of introns and exons in RNA processing?

Introns are sections of DNA and RNA that don't contain instructions for making proteins. During the process of making mRNA, known as RNA splicing, these introns are cut out, leaving behind only the exons. Exons are sections of DNA and RNA that contain the instructions for making proteins. These sequences are preserved and included in the final mRNA molecule during the process of transcription, where DNA is used as a template to produce mRNA. Exons are connected to each other to create sequences that encode proteins in a process known as ligation. The final mRNA molecule does contain any of the introns.