or indirectly with different epitopes alternatively other detection schemes for cdna may be employed such as radioisotopes electronic detection or electrochemical detection in addition mrna may be measured without conversion to cdna for example mrna may be directly measured at sample preparation step 120 subsequently at the gene expression measurement step 130 the cdnas for the control sample and the experimental samples are applied to a microarray which contains dna probes for genes for example as shown in fig4 there are dna probes for genes a b and c on a microarray 410 if a cdna sample possesses a nucleotide sequence complementary to that of a dna probe hybridization would occur upon hybridization the fluorescent intensities at each spot of the microarray may be measured with a scanning system consequently for each gene and for each experiment the expression ratio r may be calculated in various means for example r log 2 u2061 signal experiment background experiment signal control background control equation u2062 u2062 1 where signal experiment is the fluorescent intensity for a gene corresponding an experimental sample and signal control is the fluorescent intensity for the control sample corresponding to the same gene background experiment and background control are fluorescent intensities resulting from variability in overall fluorescence intensity and pixel intensity with respect to experimental sample and control sample.