What are DNA microarrays?
“DNA microarrays consist of a large number of DNA molecules that are spotted on modified glass slides, nylon membranes or silicon wafers. A microarray can contain hundreds, thousands, or tens of thousands of genes. Just as microprocessor chips enable computer users to process thousands of bits of information simultaneously, microarrays allow researchers to screen thousands of genes in a single experiment. The diameter of the spots is between 80 µm and 300 µm depending on the spotting system.
DNA Microarrays such as Affymetrix Gene Chips play an essential role in functional genomics. Such a chip contains thousands of spots consisting of short stretches of DNA. Each spot is specific for one particular gene. RNA is isolated from a cell, labelled with a fluorescent molecule, and then added to the chip. RNA molecules can bind to their specific counterpart present on the chip. The chip is then read by a high resolution scanner, and the fluorescence intensity of a spot is used to determine how strongly the gene was expressed in the cell. By comparing RNA prepared from cells in different stages of development, we can identify genes which are active under certain conditions.
