Copy Number Variants

  • Herman E. Wyandt
  • Vijay S. Tonk


The progression of cytogenetics from banded chromosomes to DNA segment dosage as detected by comparative genomic hybridization-microarray analysis (aCGH, also abbreviated as CMA) has greatly increased the frequency of positive findings and difficulties of interpretation. The technique of aCGH (Fig. 32.1) involves labeling patient and control DNA with different fluorochromes, hybridizing them to 40,000–1 million DNA segments arrayed on a glass slide or “DNA chip,” and comparing the extent of patient and control DNA hybridization signal amplitudes for each segment (Lee et al., Nature Genet suppl 39:S48–S54, 2007; Carter, Nature Genet suppl 39:S16–S21, 2007;Feuk et al., Hum Molec Genet 15:R57–R66, 1998). The DNA segments serving as probes are chosen to represent the entire genome extending through chromosomes 1–22, X, and Y, allowing graphing of hybridization signals according to chromosome band and base pair coordinates (see examples in patient discussions below). Departures of hybridization ratios from equivalency indicate duplication (patient signal greater than control) or deletion (patient signal less than control), and the number of contiguous DNA segments showing signal alterations define the extent of duplication or deletion by reference to their coordinates in the human genome sequence.


Intellectual Disability Williams Syndrome Autism Disorder Angelman Syndrome Mental Disability 
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Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.Boston University School of Medicine Center for Human GeneticsBostonUSA
  2. 2.Acupath Laboratories, Inc.PlainviewUSA
  3. 3.Department of PediatricsTexas Tech University Health Science CenterLubbockUSA

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