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Cytogenetics

It is a branch of genetics that involves the study of human chromosomes. Chromosome studies are crucial in prenatal diagnosis, in certain patients with mental retardation and multiple birth defects, in patients with abnormal sexual development, and in some cases of infertility or multiple miscarriages. Cytogenetic analysis is also useful in the study and treatment of patients with malignancies and hematologic disorders. New techniques allow for increased resolution of chromosome banding patterns, permitting differentiation of a greater number of abnormalities.

Tequniques  used in our cytogenetics lab :

Karyotyping

Karyotyping is a detailed analysis of chromosomes to detect abnormalities of the number or the structure of chromosomes. The chromosomes are obtained from peripheral blood, amniotic fluid, chorionic villi, bone marrow samples after culturing for suitable time. The metaphases are fixed on slides, Geimsa banded, mapped and analyzed for abnormalities. We have the Zeiss/Metasystems automated karyotyping workstation where images of the metaphases are captured, processed and stored. Numerical and structural chromosome abnormalities like trisomies, deletions and translocations can be detected.

FISH

Fluorescence in situ hybridization (FISH) is a new and rapid procedure to detect certain common chromosome abnormalities. We use directly labeled commercially available FISH probes which are complementary to the region of interest on a particular chromosome. The analysis is usually done by counting colored dots under a fluorescent microscope. The cells are pretreated and fixed on slides. The slides are dehydrated, co-denatured with appropriate probe, hybridized, washed and mounted in antifade solution together with counter stain. The FISH signals are observed under a Zeiss fluorescence microscope using appropriate filters and the images are captured and analyzed with the Metasystems software. FISH is also used to detect common aneuploidies and low-grade mosaicism mainly in prenatal diagnosis. Analysis by FISH is possible even on interphase nuclei.