FISH (Fluorescence In Situ Hybridization) Test

“A technique used to identify the presence of specific chromosomes or chromosomal regions through hybridization (attachment) of fluorescently-labeled DNA probes to denatured chromosomal DNA. Examination under fluorescent lighting detects the presence of the hybridized fluorescent signal (and hence presence of the chromosome material) or absence of the hybridized fluorescent signal (and hence absence of the chromosome material). With metaphase FISH, cells progress through the division process until metaphase, when chromosomes are condensed and can be individually distinguished. In contrast to interphase FISH, metaphase FISH permits visualization of the actual chromosomes as well as the general location of the abnormality on the chromosome.” – 2009 The MHE Reasearch Foundation

Basically it’s a test where they take some cells and tell you what the chromosomal make-up of the cells looks like.