Premature chromosome condensation in temperature-sensitive cells arrested in G1 phase

The structural morphology of prematurely condensed chromosomes (PCC) was used as a probe to detect accumulation of temperature-sensitive (ts) cells at different points of the G₁ phase at the non-permissive temperature (38 °C). Interphase cells of wild type Balb/c-3T3 and its ts variant clones incubated at 38 °C were fused with mitotic CHO cells. Compared to a random population of 3T3 cells, the ts variants accumulated individual grades of G₁ phase PCC. These results were in accordance with the complementation data (Naha, 1979) regarding the relative position of the variants in the G₁ phase of the cell cycle.