CYTOGENETICS FOR CONSTITUTIONAL DISORDERS
Karyotyping, also known as routine chromosome analysis, is a procedure that examines chromosomes in a sample of cells. The structure of each chromosome is analyzed for abnormalties as well the total number of chromosomes are noted. The chromosomes are then arranged in a karyogram which lists the 22 pairs of autosomes and 1 pair of sex chromosomes.
Routine chromosome analysis is a useful methodology to detect common, recurrent chromosome abnormalities for constitutional and hematological disorders. This technique has been in practice since 1956 and is a confirmed standard of care by the American Academy of Pediatrics (AAP), the American College of Medical Genetics & Genomics (ACMG), and the American College of Obstetricians & Gynecologists (ACOG).
FISH analysis is a technique that is used to detect and localize the presence or absence of specific DNA sequences on chromosomes. FISH uses fluorescent probes that are often derived from fragments of DNA that were isolated, purified, and amplified for use in the Human Genome Project. The probes bind to only those parts of the chromosome with which they show a high degree of sequence complimentarity. The cells are then viewed under the microscope to locate the site where the probe is bound to the chromosome.
This type of analysis is useful in locating deletions or duplications that are too small to be seen via karyotyping and the cost of the assay is minimal compared to other methods of genetic testing. FISH is routinely used for the diagnosis of constitutional disorders. The probes used in this assay are chromosome region specific so the clinician must specify the probe and/or the disease/syndrome they suspect or have diagnosed in the patient.
FISH ANALYSIS FOR CONSTITUTIONAL DISORDERS
FISH analysis can be performed for the following constitutional disorders:
Trisomies of chromosomes 13, 18, and 21
DiGeorge syndrome 22q11.1
Please refer to the Cytogenetics for Constitutional Disorders test order form to order testing and to review the specimen requirements.
OUHSC Genetics Laboratory 1122 NE 13th Street, Suite 1400, Oklahoma City, OK 73104
Phone (405)271-3589 Fax (405)271-7117 After hours phone (405)496-9514
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