Fluorescence in situ hybridization (FISH) with a chromosome 7 specific alpha 
satellite DNA probe was used to detect monosomy 7 in interphase and metaphase 
cells obtained from patients with myelodysplastic syndrome (MDS) and acute 
nonlymphocytic leukemia (ANLL). Chromosome analysis revealed monosomy 7, either 
alone or as part of a complex chromosome abnormality, in all cell samples. FISH 
analyses of 12 marrow samples and a blood sample using a chromosome 7 specific 
alpha satellite DNA probe revealed a single fluorescence spot in 80.5-97.5% of 
interphase cells indicating monosomy 7. In contrast, 83.5-92.0% of the same 
cells had two copies of chromosome 17 as two fluorescent spots were detected 
using a chromosome 17 specific alpha satellite DNA probe used as a positive 
control. The proportion of interphase cells with monosomy 7 did not correlated 
with the percentage of metaphase cells with monosomy 7 detected by conventional 
karyotyping or with the percentage of blast cells in the bone marrow.