In biotechnology, a component of a device for screening genomic or cDNA for mutations, polymorphisms or gene expression. A chip is a small (a few centimetres on each side) standardised glass or other solid surface on which thousands of immobilised oligodeoxynucleotide probes have been synthesised or robotically deposited in a predetermined array, so that automated recording of fluorescence from each of the spots may score successful hybridizations. A chip may be designed for the detection of all known genes of a species (human, mouse, yeast), or selected specific sequences.