A reporter gene is a gene that researchers use to study the activity of other genes. It is typically linked to a measurable trait, such as the production of a specific protein or enzyme. By inserting a reporter gene into a cell or organism, scientists can easily track gene expression and understand how genes function in different conditions. Common examples of reporter genes include green fluorescent protein (GFP) and β-galactosidase. These genes produce visible signals, allowing researchers to visualize and quantify gene activity. This technique is widely used in molecular biology, genetics, and biotechnology to investigate cellular processes and gene regulation.