X-Inactivation (X-I) Studies
|Clinical info||Determination of maternal and paternal X chromosome activation status is useful in the diagnostic analysis of nonrandom patterns. Skewed patterns of inactivation in female carriers of a number of X-linked recessive disorders and asymptomatic female carriers of some X-linked dominant diseases have been observed. By using the methylation-sensitive restriction enzyme HpaII and the polymerase chain reaction, the methylation status of both the maternal and paternal X chromosome is determined. Methylation of the HpaII restriction endonuclease site in the human androgen-receptor gene, HUMARA, correlates with X-inactivation. In approximately 10% of cases, the testing is uninformative due to the presence of the same allele size on both X chromosomes.|
|Indications||X-inactivation studies are useful in diagnosing some X-linked recessive disorders and determining carrier status of family members|
|Specimen Requirements||5 to 10 ml of peripheral blood collected in an EDTA (lavender top) Vacutainer tube is preferred. The minimal blood needed for reliable DNA isolation is 3 ml|
|Transport||The specimen should be kept at room temperature and delivered via overnight shipping. FedEx is preferred. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.|
|Turnaround time||2 weeks|
Molecular Diagnostic Lab
The Molecular Diagnostic Lab offers DNA analysis for many genetic disorders via gene sequencing, targeted mutation analysis, MLPA deletion/duplication testing, trinucleotide repeat analysis and next generation sequencing panels.