What is reporter gene? Give an example?

A reporter gene is a gene that encodes a protein whose expression can be easily monitored or detected in living cells or organisms. It is widely used in molecular biology and genetics to study gene expression and regulation. The protein product of the reporter gene is typically not endogenous to the organism under study, which allows researchers to distinguish its expression from that of the organism's own genes.

An example of a reporter gene is the green fluorescent protein (GFP), originally isolated from the jellyfish Aequorea victoria. GFP emits green light when exposed to blue or ultraviolet light. This property makes it very useful for visualizing where and when certain genes are expressed within cells or tissues. Researchers can fuse the promoter region of a gene of interest with the GFP gene, allowing them to observe the spatial and temporal patterns of gene expression in living organisms under a microscope.