8.20—Microarrays and active genes

A microarray uses labelled nucleic acids from samples to measure which genes are expressed relative to a reference. Complementary binding at spots produces a pattern that can be compared between tissues or conditions.

The result is a relative expression profile, not a direct measurement of every protein or a guaranteed cause. Controls, normalisation and probe specificity determine how confidently differences can be interpreted.

A gene spot with stronger signal in diseased tissue suggests higher transcript abundance, but follow-up experiments are needed to test whether the gene drives the phenotype.

A microarray signal is not automatically protein activity, and a difference in expression is not proof of causation.