pre-mRNA is a precursor molecule in the process of gene expression. It is synthesized from DNA during transcription and contains both coding regions, known as exons, and non-coding regions, called introns. Before pre-mRNA can be translated into a protein, it undergoes several modifications, including the addition of a 5' cap and a poly-A tail, as well as the removal of introns through a process called splicing. This results in a mature mRNA molecule that can be translated by ribosomes into proteins.