A fragment spanning nucleotides −551 to +672 of the HTR1A (Transcription start site +1) 5′ promoter region was used to construct three haplotype plasmids (1-1 to 3-1). The relative fluorescence intensity of plasmids 1-1 and 3-1 was compared to the wild type plasmid 2-1 after transfection of HEK-293 and SK-N-SH cells. In the HEK-293 cells, there was a significant difference between plasmid 1-1(GC) and plasmid 2-1(GG). A significant difference between plasmid 1-1 and plasmid 2-1 was also observed in the SK-N-SH cells.