A DNA microarray (also commonly known as DNA chip or biochip) is a collection of microscopic DNA spots attached to a solid surface. Scientists use DNA microarrays to measure the expression levels of large numbers of genes simultane A DNA microarray is a collection of microscopic DNA spots attached to a solid surface. Scientists use DNA microarrays to measure the expression levels of large numbers of genes simultaneously or to genotype multiple regions of a genome. Each DNA spot contains picomoles of a specific DNA sequence, known as probesously or to genotype multiple regions of a genome The DNA copy that is made, called complementary DNA (cDNA), is then applied to the microarray. The cDNA binds to complementary base pairs in each of the spots on the array, a process known as hybridization. ... A black spot indicates that none of the patient's cDNA has bonded to the DNA in the gene located in that spot. SAGE can determine absolute abundance of mRNAs and differences in expression levels between samples can be compared. In contrast, microarray data is specific to the format, so data sets cannot be easily compared between platforms. Microarrays are also easier to use and more suitable for high-throughput experiments