Exons are segments of DNA that contain the coding information for proteins. They are part of a gene and are 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, resulting in a mature mRNA molecule that can be translated into a protein. In the context of eukaryotic cells, exons play a crucial role in determining the final structure and function of proteins. The arrangement and combination of different exons can lead to the production of various protein isoforms, allowing for greater diversity in protein function and regulation within an organism.