Marker gene is a term used in molecular biology, which refers to a gene that provides a visible or measurable trait that can be used to identify cells or organisms. However, there are several synonyms for the term marker gene, including reporter gene, selectable marker, and indicator gene. A reporter gene is a genetic marker used to report the expression of a specific gene, while a selectable marker is a gene that allows cells to be selected for a specific characteristic. An indicator gene is a gene that can be used to indicate the presence or activity of a specific enzyme or pathway. These synonyms for marker gene play a crucial role in genetic engineering and gene therapy research.