Cytogenetic abnormalities, detection

Detection of specific cytogenetic abnormalities For instance, a small deletion of band Xp21.2 was important in cloning the gene involved in Duchenne muscular dystrophy. 

An international effort is underway to harmonize methodologies for detecting BCR-ABLl transcripts and kinase domain mutations and adjusting the results so they are standardized from one lab to another (28,29). The availability of a reproducible real-time quantitative PCR (RQ-PCR) has shown in one study that patients with a major molecular response do not have evidence of cytogenetic abnormalities in their bone marrow, and therefore a policy of performing bone marrow biopsies only in patients who have not achieved or have lost a major molecular response would allow many patients to forego the discomfort and expense of multiple bone marrow biopsies (30). 

FISH. Fluorescent in-situ hybridization a method utilizing fluorescently labeled DNA probes to detect or confirm gene or chromosome abnormalities that are generally beyond the resolution of routine cytogenetics. 

An evaluation of occupational chemical exposure, histological subtype, and cytogenetics was conducted on case studies of newly diagnosed AML or CML, or myelodysplastic syndromes (MDS) treated in the Main Hospital of Torino, Northern Italy, between October 1, 1989 and December 31, 1990 (Ciccone et al. 1993). There was a nonstatistically significant increased relative risk for exposure to benzene. Data show 3 AML, 2 CML, and 4 MDS cases with regard to benzene exposures. No excess of clonal chromosome abnormalities was detected among occupationally exposed AML patients. 

Cytogenetics is the oldest of the medical genetic sciences, but it did not become important clinically until 1959, when the presence of an extra copy of chromosome 21 (Trisomy 21) was first implicated in Down syndrome. Since then, many other chromosomal abnormalities have been directly associated with different diseases. By viewing metaphase cells with the light microscope, trained personnel can detect a broad range of numerical and structural chromosome anomalies that can then be correlated to specific diagnoses ranging from Down syndrome and Thrner syndrome to various types of cancer. 

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