A DNA microchip or gene chip is a tiny chip that has many single strands of the DNA from a specific gene attached to it. Sometimes a microchip has more than one gene's DNA on it or different variations of a gene. It is used to test for gene mutations, such as the ones that are thought to be responsible for a larger percentage of hereditary breast cancer cases.
Fragments of denatured complementary DNA from a test subject are marked with green, fluorescent tags, and control DNA is marked with red. These are added to the microchip to bind with the DNA already in place. If the microchip is an even mix of red and green, the test subject doesn't have a mutation. If only red is visible, the test subject does have a mutation in that gene.