| General Information: |
Fluorescence in situ hybridization (FISH) is a molecular cytogenetic technique that can detect chromosomal abnormalities that cannot be appreciated by standard chromosomal analysis (e.g. microdeletion syndromes) or when mitotic cells are not available for chromosomal analysis (e.g. X/Y FISH for cross-sex transplants). Briefly, metaphase chromosomes or interphase nuclei are denatured on the slide, as is the fluorescently labeled DNA probe. The probe and the chromosomes/nuclei are then hybridized; slides are washed, counterstained and analyzed by fluorescent microscopy. There are a number of different types of FISH probes including unique sequence probes (e.g. microdeletion syndromes), whole chromosome painting probes, repetitive probes (e.g. centromeric alpha satellite probes, subtelomeric probes), gene fusion probes (e.g. BCR/ABL in t(9;22) in CML and ALL) and break apart probes (e.g. MLL in 11q23 rearrangements in ALL and AML).
Typically, FISH for congenital anomalies is performed on metaphase chromosomes from PHA-stimulated peripheral blood samples. However, FISH can be performed on metaphases from any tissue type. |
