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Colorado Genetics Laboratory

FISH for Gender Determination


FISH for gender determination is indicated to screen for sex chromosome identification in an infant with ambiguous genitalia, in conjunction with standard blood chromosome analysis.


FISH studies involve analysis of hybridization signals using chromosome-specific DNA probes on interphase nuclei.

Chromosome studies are performed concurrently with FISH testing, if they have not been done previously.

Specimen Requirements

Since FISH for gender determination is done in conjunction with chromosome analysis, no additional specimen is usually required. See specimen requirements for appropriate chromosome analysis.

Sample must be accompanied by a completed Test Request Form​​, including pertinent clinical and family history.​