Comparative Genomic Hybridization

Abstract

Comparative genomic hybridization (CGH) is a modified in situ hybridization technique which allows detection and mapping of DNA (deoxyribonucleic acid) sequence copy differences between two genomes. In CGH analysis, two differentially labelled genomic DNA (study and reference) are cohybridized to normal metaphase spreads or to microarray. Chromosomal locations of copy number changes in the DNA segments of the study genome are revealed by a variable fluorescence intensity ratio along each target chromosome or DNA sequences. Thus, CGH allows detection and mapping of DNA sequence copy differences between two genomes in a single experiment. Since its development, CGH has been applied as a research tool in the field of cancer cytogenetics to identify genetic changes in many previously unknown regions. CGH is also a powerful tool for detection and identification of unbalanced chromosomal abnormalities in prenatal, postnatal and preimplantation diagnostics. Array CGH is a high‐resolution technique to detect chromosomal DNA copy number variations at a genome‐wide scale.

Key concepts

  • Comparative genomic hybridization is a modified in situ hybridization technique.

  • CGH allows detection and mapping of DNA sequence copy differences between two genomes.

  • In CGH analysis, two differentially labelled genomic DNA segments (study and reference) are cohybridized to normal metaphase spreads or to mapped DNA sequences or oligonucleotides arrayed onto glass slides (array CGH).

  • Chromosomal locations of copy number changes in the DNA segments of the study genome are revealed by a variable fluorescence intensity ratio along each target chromosome.

  • In CGH on chromosomes, genetic changes are detected and mapped on chromosomes.

  • CGH allows the detection and characterization of whole and partial aneuploidies.

  • CGH has been widely used for the study of chromosomal imbalances in tumours.

  • An important contribution of CGH to cancer research has been in pinpointing putative locations of cancer genes.

  • In clinical genetics, CGH is increasingly used in diagnosing unbalanced chromosomal rearrangements.

  • Since its development, CGH has been applied mostly as a research tool in the field of cancer cytogenetics, but it is also used in clinical genetics.

Keywords: hybridization; molecular cytogenetics; chromosomes; CGH; fluorescence

Figure 1.

Schematic diagram of the comparative genomic hybridization (CGH) technique. Study and reference DNA segments are labelled with a green and red fluorochrome, respectively, and hybridized with human Cot‐1 DNA to normal metaphase spreads or on mapped DNA sequences or oligonucleotides arrayed onto glass slides.

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References

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Further Reading

Appasani K (2007) Bioarrays: From Basics to Diagnostics. Totowa, NJ: Humana Press.

Fan YS (2002) Molecular Cytogenetics: Protocols and Applications. Totowa, NJ: Humana Press.

Fuchs J and Podda M (2004) Encyclopedia of Medical Genomics and Proteomics. New York: Informa HealthCare.

Gersen SL and Keagle MB (2004) Principles of Clinical Cytogenetics. Totowa, NJ: Humana Press.

Swansbury J (2003) Cancer Cytogenetics: Methods and Protocols. Totowa, NJ: Humana Press.

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How to Cite close
Tachdjian, Gérard(Sep 2009) Comparative Genomic Hybridization. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0002651.pub2]