The Human Genome Project has identi-fied,along with single nucleotide polymorphisms(SNPs),a range of other DNA sequence variations,including insertions and deletions of nucleotides and translocations of various segments of a chromosome.1 These variations have,collectively,been named copy number variants(CNVs).1 They represent a major source of genomic variation,with nearly 1500 variable regions covering approximately 12%of the human genome.2 A CNV could act directly by affecting gene dosage and gene expression through complex mechanisms.It is thought,therefore,that CNVs in genedosage sensitive genes may have considerable influence on disease susceptibility.2 Among genes overlapped by CNVs,significant enrichments in certain gene ontology categories have been identified,including those related to immune responses and interaction with the environment.3 CNVs have already been associated with several monogenic,syndromic and complex diseases.
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