The data are then stored as digital images. If it is known which genes the immobilized sequences represent, then the hybridization pattern identifies the genes that are expressed differently in the tissue after chemical treatment. Before the advent of microarray technology, the collection of either qualitative or quantitative data on the expression of genes was an intensive and laborious task. With large-scale gene expression detection technologies, scientists may quickly examine the activity of potentially all the genes in an organism under differing conditions to identify those that are of most interest and merit further study. DNA microarrays have the potential to be used in a variety of ways in toxicology, including identifying biomarkers of exposure and determining how a particular chemical causes toxicity.
All substances have a threshold at which they are toxic.
The dose determines the toxicity. There are a lot of changes that could be going on at lower doses or earlier times that have nothing to do with toxicity. When you look at one dose or one time, you wouldn't see all those changes. Looking at a single time or single dose doesn't reveal the genes that are linked to the toxicity. Corton believes that before DNA microarrays will be maximally useful for characterizing the toxic effects of unknown chemicals, a database cataloging the toxic effects of model compounds must be constructed.