Centromeric index measurement by slit‐scan flow cytometry

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Abstract
We report here the application of slit‐scan flow cytometry (SSFCM) in the classification of muntjac, Chinese hamster, and human chromosomes according to centromeric index (CI) and total flurescence. Chromosomes were isolated from mitotic cells, stained with propidium iodide and processed through the SSFCM where flurescene profiles were measured. The centromere for each profile was taken us the point of maximum difference between the measured profile and a standard profile having no centrmeric dip. The areas under the profile on eithr side of the centromere were then calculated and the CI was calculated as the ratio of the larger area to the total area under the profile. Relative DNA contents for each chromosome were taken to be proportioned to the total fluorescence. Mean CI's for muntjac chromosomes 1, 2, and × + 3 were 0.52, 0.88, and 0.73, respectively; CI's for Chinese hamster M3‐1 chromosomes 1, 2, 5, 8, and M2 were 0.53, 0.55, 0.77, and 0.86, respectively; and average CI's for chromosome groups 4 + t (X;5), 6 + 7 + Y, 9 + M1, and 10 + 11 were 0.56, 0.82, 0.82, 0.58, and 0.60, respectively. These results were, on average, within 4.4% of CI measurements made by image cytometry. CI's measured for human chromosomes 9 through 12, were, on average, within 2.0% of those made by image cytometry.