Biotechnology and Bioinformatics (1+1)

4.2.3.1. Principle of microarrays

· Hybridization between two DNA strands, the property of complementary nucleic acid sequence s to specifically pair with each other by forming hydrogen bonds between complementary nucleotide base pairs .

· A high number of complementary base pairs in a nucleotide sequence means tighter non- covalent bonding between the two strands.

· After washing off of non-specific bonding sequences, only strongly paired strands will remain hybridized.

· So fluorescently labeled target sequences that bind to a probe sequence generate a signal that depends on the strength of the hybridization determined by the number of paired bases, the hybridization conditions (such as temperature), and washing after hybridization. Total strength of the signal, from a spot (feature), depends upon the amount of target sample binding to the probes present on that spot.

· Microarrays use relative quantization in which the intensity of a feature is compared to the intensity of the same feature under a different condition, and the identity of the feature is known by its position.