A single nucleotide polymorphism (SNP) is a variation at a single site in DNA. It is the most frequent type of variation in the genome. Approximately 50 million SNPs have been identified in the human genome. A SNP array is able to detect changes in a person’s chromosomes, such as gains or losses. 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. Genetic similarity is an area of the chromosome that does not show the normal differences we expect to see between the material passed down 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. 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).
SNP may be ordered for anyone with dysmorphic features,
unexplained mental retardation/developmental delay,
congenital anomalies not specific to a genetic syndrome, seizures, speech delay, multiple miscarriages, tumor analysis to aid in diagnosis, and any patient with normal chromosome analysis.
Methodology: SNP (single nucleotide polymorphism)
Purpose: Confirmation of Clinical Diagnosis; strong suspicion of cytogenetic abnormality in patient who had a normal array CGH result.
Test Requisition: Molecular Requisition-Refer to diagnosis list on page 2 before ordering
CPT Code: 81229 Cost: $1905.00
Turn-around-time: 28 days
1. Sherry ST, Ward MH, Kholodov M, Baker J, Phan L, Smigielski EM, Sirotkin K. (2001) “dbSNP: the NCBI database of genetic variation:. Nucleic Acids Res. 29:308–311.