DNA microarray, illustration. DNA (deoxyribonucleic acid) microarray technology allows biologists to study thousands of genes at once. An array of DNA sequences for a particular set of genes is created, fixed to a supporting slide or chip. Each gene's position in the array is known. Samples of unbound DNA or mRNA (messenger RNA) are then labelled with differently-coloured fluorescent markers and added to the chip. The genetic material in the samples binds to sites on the array which have a matching (complementary) sequence. The pattern of colours is then analysed. Microarrays can be used to study gene expression or detect mutations.