Oligonucleotide Array: a "DNA Chip"

    An oligonucleotide array consists of a series of short (typically 20~30 bases) single-stranded DNA sequences (oligonucleotides, or "oligos") attached to a glass chip about the size of a microscope cover slip.  In the arrangement shown here, each adjacent oligo differs from its neighbor only at the last base. In the example, the first four oligos in block 1 at the lower left begin with GAGCCAAGCTG and end with A, G, C, or T, respectively.