Briefly, the GeneChip is used as follows:

• Doublestranded cDNA is synthesized from total RNA purified from the tissue under investigation.
• cRNA, tagged with biotin, are transcribed from the double-stranded cDNA.
• Tagged cRNA molecules are hybridized with the oligonucleotide probes (with known sequences) on the GeneChip.
• Unhybridized cRNA is washed away, and the hybridized, biotin-tagged cRNA reacts with streptavidin-phycoerythrin conjugate.
• A laserscanner read-out shows which of the chip-oligonucleotide probes that have hybridized to the cRNA molecules.
• The computer software automatically calculates average difference values.

Reference (for abstract, see Lists of IIR Publications):

Rieneck K, Bovin LF, Josefsen K, Buschard K, Svenson M, Bendtzen K. Massive parallel gene expression profiling of RINm5F pancreatic islet b-cells challenged with interleukin-1b. APMIS 2000;108:855-872.