Dr. Array

Modern DNA array technology evolved from colony hybridization methods developed in the 1970s. It uses thousands of DNA probes bound to a glass slide to identify DNA fragments (labeled with fluorescent dyes) in a sample that hybridizes with the probes (oligonucleotides in nature) and is detected by measuring the intensity of fluorescence. The scanner measures this fluorescence.

DNA microarrays are used to identify changes in gene expression or for detection of single nucleotide polymorphism - variants that may be different among individuals and contribute to different phenotypes observed. One example is the PTC gene TAS2R38 that codes for a taste receptor. Some of the individuals find the taste of PTC bitter, while others find it tasteless. It is because of a change in a single nucleotide that creates these two different forms of the TAS2R38 gene. Not all variants may lead to a change in the function of the gene or cause an easy to detect change that can be identified without looking at the sequence of the DNA. 

Microarrays can identify DNA/RNA which have already been identified. It measures the comparative levels of DNA/RNA using fluorescence. To identify novel and unknown variants, genes, SNPs, sequencing is the technique that is used.