mRNA expression refers to the process by which genetic information encoded in DNA is transcribed into messenger RNA (mRNA) molecules, which are then translated into proteins. Studying mRNA expression can provide insights into gene regulation, cellular functions, and disease mechanisms. Researchers use various techniques such as RNA sequencing and quantitative PCR to quantify mRNA expression levels and identify differentially expressed genes. This information can help researchers understand how genes are activated or repressed in different biological conditions, and how these changes contribute to normal physiology or disease pathogenesis.