Microarray CGH is a new and powerful high-resolution test that can detect the imbalances of chromosomes in much final detail than achievable by conventional chromosome testing. A comprehensive high-resolution test for small chromosomal imbalances (duplications and deletions) can now be preformed in a single test. Microarray CGH works by comparing the levels of patient DNA to levels of control (normal) DNA sample, see figure below.

Patient DNA and Control DNA are colored green and red, mixed together, and then placed onto a microarray slide, which contains spots of human genes for analysis. The microarray is analyzed and the relative color change (green and red) of the spots is measured to determine chromosomal imbalance. If a spot shows the same amount of green and red DNA then there is no chromosome imbalance. A duplication is shown by a greener spot. In contrast, a deletion is shown by a more red spot.

This image shows patient (green) and control (red) DNA that is mixed and placed onto the microarray slide. Analysis of the relative amounts of patient (green) and control (red) DNA shows whether there is a chromosome duplication or deletion.