Array Cgh

The test and reference DNA compete for binding to the same genomic probes. A higher fluorescence contribution from the test sample indicates increased DNA dosage at that region, whereas a lower contribution suggests decreased dosage. Because thousands of probe measurements are evaluated across chromosomes, the resulting pattern can localize copy-number changes rather than merely indicate that an imbalance exists.

Each probe represents a defined genomic location, so the collection of probe signals creates a detailed dosage profile across the chromosomes. The large number of probes allows array CGH to detect smaller or more precisely localized copy-number changes than conventional chromosome analysis. Probe-based measurements therefore help researchers examine genome structure at a finer scale.

Array CGH measures DNA dosage across thousands of genomic locations, while conventional chromosome analysis provides a broader view of chromosome organization. This difference gives array CGH higher resolution for identifying deletions and duplications. The method is therefore useful when a biological condition may involve a genomic imbalance that is too small or localized for conventional chromosome-level examination.

A typical workflow begins with DNA from a test sample and a reference sample. The two DNA preparations receive different fluorescent labels and are then allowed to hybridize competitively to genomic probes on a microarray. After hybridization, fluorescence signals are compared across the probe set, producing ratios that indicate regions of increased or decreased DNA dosage.

Array CGH is especially relevant when researchers need to investigate genome-wide copy-number changes associated with developmental disorders, cancer, or other biological conditions. Its broad chromosome coverage and relatively high resolution support the search for genomic imbalances that may contribute to a phenotype. The resulting dosage patterns can guide studies of disease-associated genome changes.

The technique provides a genome-wide profile of DNA copy-number variation, including regions with losses or gains. These patterns can be used to study genome structure, explore mechanisms underlying disease, and characterize genetic variation between a test sample and a reference sample. In biology, the measurements connect changes in DNA dosage with broader cellular or organismal conditions.