An approach was developed in controlling the expression ratio of two genes encoded in DNA by inserting a terminator sequence between the two genes. Escherichia coli ribosomal RNA operon T1 terminator, or E. coli tryptophane attenuater was introduced between two green fluorescent protein (GFP) mutants: ultraviolet-optimized mutant (GFPuv: F99S, M153T, V163A) and blue-shifted mutant (BFP: F64L, S65T, T145F). The ratio of the fluorescence intensity of BFP to GFPuv after transcription and translation reflected the termination efficiency of the transcriptional termination activity of the inserted terminator.