A reporter gene can be used to monitor the transformation of host cells by foreign DNA by keeping a track of its receptor gene. It act as a selectable marker to determine whether the host cell has taken up the foreign DNA or the foreign gene gets expressed in the cell.  The reporter gene and the foreign gene are placed in the same DNA construct and then inserted in the cell. Here, the reporter gene is used as a selectable marker to find out the successful uptake of foreign genes. An example of reporter genes includes lac Z gene, which encodes a green fluorescent protein in a jelly fish.