Fluorescent marker genes

• Fluorescent marker genes can also be used to identify the presence of a gene within a bacterial cell. This method involves the transfer of a gene which produces a green fluorescent protein (GFP) from a jellyfish to a bacterial cell.
• When is gene is to be cloned, it is transplanted into the centre of the GFP gene. Any bacterial cell that takes up the plasmid with the gene that is being cloned will not be able to produce GFP, whilst those that haven't taken up the gene will still be able to produce fluorescent colour.
• There is an observable difference between the bacteria that have and haven't taken up the gene to be cloned - the bacteria that possess the plasmid containing the desired gene will not produce a green fluorescence, and those that don't will produce a green fluorescence.
• Since the bacterial cells containing the desired gene are not killed in the process using fluorescent marker genes, there is no need for replica plating. Instead, results can simply be obtained by observing the bacteria under the microscope and keeping those which don't have any fluorescence.