Elsevier Pathology

Clinical Pathology: Genetic Testing

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• Array comparative genomic hybridization (aCGH) or chromosomal microarray analysis (CMA) is a method used to detect the differences in copy number or dosage of a particular DNA segment between two different DNA samples: the patient sample and the reference DNA sample. This is a rapidly emerging technique in clinical cytogenetics.

• This method is used to detect any unbalanced chromosome abnormalities. Unbalanced abnormalities include gains and losses of (1) entire chromosomes (aneuploidy), (2) small individual segments of DNA that cannot be detected by standard chromosome analysis, (3) extra supernumerary marker chromosomes (SMCs), and (4) ring chromosomes. This method is used in both constitutional and cancer cytogenetics.

• Depending on the resolution of the chip (the number of probes or oligonucleotides and the spacing between the probes or oligos across the genome), small deletions or duplications can be identified with detailed information about the genomic region involved: size, base positions, number of genes, and genomic content.

• Truly balanced chromosome rearrangements, such as inversions and balanced translocations, cannot be detected by this method.

• This method has revealed previously unappreciated normal variation in the number of copies of DNA segments known as copy number variants (CNVs).

Tools of human molecular genetics.In: Nussbaum RL, McInnes RR, Willard HF, eds. Thompson & Thompson Genetics in Medicine. 7th ed. Philadelphia: Saunders Elsevier, 2007:41–58.

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