Molecular markers
Microarray variations
Comparative genomic hybridization




Topic Completed: 1 July 2010

Revised: 15 February 2019

Copyright: 2008-2018, PathologyOutlines.com, Inc.

PubMed Search: Comparative genomic hybridization[TI] microarray[TI]

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Cite this page: Shackelford R. Comparative genomic hybridization. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/molecularpathmicroarraygenomic.html. Accessed June 16th, 2019.
Definition / general
  • Comparative genomic hybridization (CGH) is used to detect copy number changes (amplifications or deletions) of relatively large genomic segments
  • CGH only detects unbalanced chromosomal changes; balanced chromosomal alterations, such as inversions and translocations are not detected, as no change in copy number occurs
Methodology
  • Control DNA is taken from cells with a normal karyotype and compared to the sample to be examined
  • Examined sample is often from a tumor or tissue from a child with dysmorphic features who is likely to have unknown genomic amplifications or deletions
  • Originally, CGH was done with fluorescent labeled metaphase chromosomes immobilized on glass slides, cohybridized with different fluorescent labeled control and sample DNA
  • Comparison of the different preparations and fluorescent labels allows the identification of changes in the copy number along specific chromosomal regions
  • Resolution of this approach is low, allowing only changes of 20 Mb or more to be identified (Dufva: DNA Microarrays for Biomedical Research, 2009)
  • Currently array CGH is more commonly used to analyze amplifications or deletions between sample and control cells; it uses an immobilized probe array, to which are hybridized differently labeled normal and sample DNAs; the resolution depends upon the number of immobilized probes employed
  • CGH allows only the comparison of the relative ratio of different DNA segments between samples and controls, not the ploidy; thus, comparing two tetraploid clones lacking amplifications or deletions by CGH would give a normal result
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