Precursor mRNA, or pre-mRNA, is an initial form of messenger RNA synthesized from a DNA template during the process of transcription. It contains both coding regions, known as exons, and non-coding regions, called introns. Pre-mRNA undergoes several modifications before it becomes mature mRNA, which is ready for translation into proteins. The modifications include the addition of a 5' cap and a poly-A tail, as well as the removal of introns through a process called splicing. These changes are essential for the stability and functionality of the mRNA, ensuring that the correct protein is produced in the cell.