Northern and microarray comparison. A series of 75 Northern blots with total RNA from germline-less ('tud') male, wildtype (y1w67c) male, germline-less ('tud') female and wildtype (y1w67) female whole flies were probed with the PCR products identical to those printed as microarray elements. (a) 34 Northern blot images show a range of expression patterns among the input RNA samples. Phosphorimaging of the radioactive signal from Northern blots gave expression ratios between the RNA sample types for each Northern probe. (b-e) Corresponding (Ln) transformed Northern and microarray element ratios averaged from multiple experiments are shown as four scatterplots comparing expression between (b) y1w67cmales versus y1w67cfemales; (c) 'tud' males versus 'tud' females; (d) y1w67cmales versus 'tud' males and (e) y1w67cfemales versus 'tud' females. The y and x axes are expression ratios derived from Northern blot and microarray ratios respectively. Over two-, over four- and over tenfold differences in ratio values between the Northern and microarray experiments are indicated in yellow, red and blue.