A chromosome SNP (single nucleotide polymorphism) array is a genetic test that is able to detect changes in a person’s chromosomes, such as gains (duplications) or losses (deletions). These gains or losses result in extra or missing copies of genetic material. Changes in a person’s chromosomes may be associated with known genetic conditions or may cause problems with health and development.

The SNP array can also detect genetic similarity (runs of homozygosity). Genetic similarity is an area of the chromosome that does not show the normal differences we expect to see between the material passed down (inherited) from the mother and the father. If multiple regions of genetic similarity are found by the SNP array, that person’s parents might be more closely related than originally thought (called consanguinity). For example, the parents might be related like cousins. If a region of genetic similarity is found, it could provide a clue to a specific genetic condition and more genetic testing may be recommended.

The SNP array test does not detect all differences in the chromosomes or DNA. For example, it cannot detect rearrangements in the chromosomes that do not cause extra or missing copies of genetic material (balanced chromosome rearrangements) and cannot detect small changes in the DNA (point mutations).

Those providing pre-test counseling must be aware that our lab will report copy number changes involving deletions and duplications of loci that can cause or predispose to adult-onset disorders and some cancer predisposition syndromes.