Abstract A line of mouse myeloid leukemic cells in culture contained two types of clones. One type can be induced by the differentiation‐inducing protein MGI to undergo normal differentiation to mature macrophages and granulocytes (D + clones), whereas the other type could not be induced to differentiate (D − clones). D + clones can segregate some D − progeny and D − clones can segregate some D + progeny. The segregant clones were more unstable in their ability to differentiate, than the stable parental clones from which they were derived. The chromosome banding pattern has been analyzed in 10 stable and six unstable clones. The clones had a modal chromosome number of 39, 40 or 41, and none of the clones, not even those with 40 chromosomes, showed a normal diploid banding pattern. Stable D + and D − clones had different karyotypes. However, the banding patterns of the unstable D + and D − segregants were not detectably different from the parental clones from which they were derived. The results indicate that normal differentiation can occur in aneuploid myeloid leukemic cells; that the initial segregation from D + to D − and from D − to D + was due to a hereditary change which did not show chromosome changes detectable by the banding technique; and that detectable chromosome changes were associated with hereditary stabilization of the difference between D + and D − .
Hayashi et al. (Mon,) studied this question.