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Why do fluorescent spots appear on a microarray during gene-expression analysis?

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Computer-generated model of anthrax toxin showing seven differently colored protein units, with a small gold molecule representing a drug bound to the protein structure. — bioinformatics This computerized image of anthrax shows the various structural relationships of seven units within the protein and demonstrates the interaction of a drug (shown in yellow) bound to the protein to block the so-called lethal factor unit. Bioinformatics plays an important role in enabling scientists to predict where a drug molecule will bind within a protein, given the individual structures of the molecules.

Fluorescent spots appear on a microarray during gene-expression analysis because the probes on the chip have been hybridized with labeled molecules from a sample.12

In this process, messenger RNA (mRNA) extracted from a sample is typically converted into complementary DNA (cDNA) and labeled with a fluorescent tag. When the microarray is bathed in this labeled solution, the molecules bind (hybridize) to their corresponding gene probes fixed to the chip's surface. After washing away any unbound material, the chip is scanned using laser-based technology. The resulting fluorescent spots indicate the presence and relative quantity of specific mRNA transcripts, allowing researchers to define the transcriptome and measure gene expression or repression.12