Dna Microarrays

By examining where and when genes are expressed in a cell or organism, one can acquire valuable hints to its function, for genes compile the genetic make-up of an organism and exploring the function of genes is helping to uncover the complexity of ourselves and of other forms of life (1). Significant developments have been made in gene monitoring techniques specifically in DNA microarrays which only very recently revolutionized genome expression analysis (1). Despite continuous improvements and modification to the technique, DNA microarrays are still no more than a glass microscope slide studded with individual immobile nucleotide fragments (1, 2). The fundamentals of DNA microarrays are set on complementary base-pairing (3), and because the exact sequence and position of every segment on the slide is known, each serves as a probe for a specific gene (1).
The two main microarray systems are spotted DNA and oligonucleotide arrays (4); there are others with various difference but all are essentially derived from the same simple design (3). Messenger RNA from the cells of interest is first converted into cDNA which is then labeled with a fluorescent probe and incubated with the microarray where hybridization occurs; positions of hybridization are detected with a scanning-laser microscope (1). For comparison studies, typically two differently labeled samples (a test and a control) are mixed and the scanned intensity of each dye is proportional to the amount of hybridization by the respective cDNA (4). Regardless of simplicity, what makes microarrays truly ground-breaking is its ability to analyze thousands of nucleotides in a single assay as opposed to blotting techniques (5). This high capacity in turn saves both time and resources (4). It should also be noted that the technology allows for the interaction of different molecular pathways to be studied simultaneously and the degree of specificity is so fine-tuned that subtle differences are more easily detected