What are exons?

Exons are the coding regions of a gene that remain in the final messenger RNA (mRNA) transcript after the process of splicing. During gene expression, the initial RNA transcript, known as pre-mRNA, contains both exons and introns (the non-coding regions). To produce a functional mRNA that can then be translated into a protein, the introns are removed in a process called splicing, leaving only the exons to be joined together.

The key role of exons is to specify the amino acid sequence of a protein, as they correspond to the actual coding sequences that will be translated during protein synthesis. This underscores the importance of exons in the overall process of gene expression and regulation of proteins in living organisms.