What are the types of microarrays based on the mode of preparation?

The three types of microarrays based on the mode of preparation are spotted arrays on glass, self-assembled arrays, and in-situ synthesized arrays. With spotted arrays, a pen (or multiple pens) is dipped into the solution holding the DNA of interest. Then it is applied on a 1” X 3” glass microscope slide. Spotted arrays are produced on poly-lysine coated glass microscopic slides, a silane, or a chemically reactive surface. This allows for binding of high-density DNA by using slotted pins and for fluorescent labeling of the sample. Self-assembled arrays are fiber optic arrays produced by the deposition of DNA synthesized on small polystyrene beads containing differing sets of oligos. The beads are deposited on the etched ends of the array, on pits the size of the beads. After the array is produced, a series of hybridizations determine which oligo is in what position on each array. Different DNA can be produced on different beads and using a mixture of beads on the fiber optic cable will make a randomly assembled array. In-situ synthesized arrays are made by chemical synthesis on a solid substrate. In the chemical synthesis process, photolabile protecting groups are combined with photolithography to carry out the function. These arrays are utilized for genotyping, sequencing, and expression analysis.