These variations in gene expression are at the core of altered physiologic and pathologic processes. DNA array technologies provide rapid and cost-effective methods of identifying gene expression and genetic variations. DNA microarrays typically consist of thousands of immobilized DNA sequences present on a miniaturized surface the size of a business card or less. Microarrays are distinguished from macroarrays in that the DNA spot size is smaller, allowing the presence of thousands of DNA sequences instead of the hundreds present on macroarrays. In this text, array generally refers to microarrays.
Robotic technology is employed in the preparation of most arrays.
The DNA sequences are bound to a surface such as a nylon membrane or glass slide at precisely defined locations on a grid. Using an alternate method, some arrays are produced using laser lithographic processes and are referred to as biochips or gene chips. These arrays are frequently used in genotyping experiments. DNA samples are prepared from the cells or tissues of interest. The DNA samples are tagged with a radioactive or fluorescent label and applied to the array.