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Unit Code 80601:
XX/XY in Opposite Sex Bone Marrow Transplantation, FISH

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Method Description

FISH is performed using directly labeled, multicolored fluorescent

DNA probes specific for the X chromosome centromere and the

distal portion of the Y chromosome long-arm. FISH is performed

by placing the probes on microscope slides with the cells from the

specimen to be studied. The DNA of the probes and cells are

denatured at 70 degrees C for 2 minutes. The probe and chromosomal DNA

are then allowed to hybridize overnight at 37 degrees C. The cells

are washed with post-hybridization solution to remove excess probe

DNA and hybridization solution. With this method, XX cells have 2

orange (X chromosome) signals and XY cells have a single orange

(X chromosome) and a single green (Y chromosome) signal. The

FISH studies involve analysis of 500 interphase cells and up to 5

metaphase cells. The number of donor and recipient cells is

expressed as a percentage of the total number of interphase cells

analyzed. Greater than 0.6% XX cells in a female recipient or >0.3%

XY cells in a male recipient are regarded as evidence for the

presence of residual recipient cells. (Dewald GW, Schad CR,

Christensen ER, et al:  Fluorescence in situ hybridization with X

and Y chromosome probes for cytogenetic studies on bone

marrow cells after opposite sex transplantation. Bone Marrow

Transplant 1993;12:149-154)

Performing Laboratory Location

Rochester

Key