The chinese hamster Don cell line differs from normal diploidy by one chromosome band.

G-banded and C-banded prometaphase and metaphase karyotypes of the Chinese hamster Don cell line from three different laboratories were compared. All the cell lines were pseudodiploid. Each consisted of two distinct cell populations designated S1 and S2. The chromosome complements of each of these populations differed from the diploid by only one additional chromosome band on a subterminal 1p in S1 and on a median 1q in S2. The sites of these extra bands were neither constricted nor heterochromatic. All other different karyotypes, including those from seven distinct subpopulations, had basic patterns of chromosome complements that were best represented by S1 or S2, respectively the major or minor cell type of the cell line. Moreover, nearly 80% of the metaphases analyzed had a modal chromosome number of 22, and about 60% had the same chromosome composition of a cell type or subtype. Our data also suggest that Don cells were probably pseudodiploid by 1964 or before.