Exons are the segments of a gene that contain the coding information necessary for producing proteins. They are part of the DNA sequence that is transcribed into messenger RNA (mRNA) during the process of gene expression. After transcription, exons are spliced together, while non-coding regions called introns are removed. In the final mRNA molecule, exons determine the sequence of amino acids in a protein. This sequence is crucial because it influences the protein's structure and function. Understanding exons is essential for studying genetics, molecular biology, and the mechanisms of diseases related to gene mutations.