Arrays cannot deal well with repetitive sequences but are extremely good at checking for mutations.
In practice, the hybridizations are all carried out at once. There are actually 65,536 possible eight-base sequences. Samples of each of the eight-base sequences to be used as probes are arranged in a square array and anchored to the surface of a glass chip. The glass chip can then be dipped in a solution of the target DNA, which will hybridize simultaneously to all those eight-base sequences with which it has complementary sequences. Instead of nucleotide array detector, the array is simply called a DNA chip. The technology is so precise that an array about 1 cm square can carry up to a million nucleotide probe sequences.
For example, if the unknown sequence of DNA is TCCAACGATTAGTCG, then its complementary strand will be AGGTTGCTAATCAGC. Consequently, of all 65,536 possible eight-base sequences, only the following can hybridize with the original sequence:
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