What is the Difference Between CGH and Array CGH?

Comparative genomic hybridization (CGH) and array CGH (also known as aCGH) are molecular cytogenetic techniques used to detect chromosomal copy number changes on a genome-wide scale. The main difference between the two methods lies in the target used for analysis and the resolution they offer.

CGH:

• Uses metaphase chromosomes as the target for analysis.
• Has a lower resolution, typically limited to alterations of approximately 5-10 Mb.
• Does not require cells undergoing division.

Array CGH:

• Uses slides arrayed with small segments of DNA (such as oligonucleotides, cDNAs, or genomic fragments cloned in various vectors) as the targets for analysis.
• Offers a higher resolution, with the standard resolution varying between 1 and 5 Mb, and the ability to increase up to approximately 40 kb by supplementing the array with extra clones.
• Also does not require cells undergoing division.

Both CGH and array CGH compare the patient's genome against a reference genome to identify differences and locate chromosomal imbalances. However, array CGH overcomes the limitation of low resolution associated with conventional CGH by replacing metaphase chromosomes with smaller, well-defined DNA segments. This results in a higher resolution and the ability to detect smaller chromosomal alterations.

Comparative Table: CGH vs Array CGH

CGH (Comparative Genomic Hybridization) and Array CGH are two molecular cytogenetic techniques used to detect unbalanced chromosomal abnormalities and copy number variations in individuals. Here is a table comparing the differences between CGH and Array CGH:

In summary, CGH is a traditional method for analyzing copy number variations, while Array CGH is a more advanced, fully automated technique with higher resolution and sensitivity. Both methods are used for comparative genomic analysis and detecting genetic disorders due to copy number variations.