We created a heterokaryon by mating two yeast strains containing a kar mutation that prevented their nuclei from fusing together. One nucleus contained a recognition site for the HO endonuclease while the second did not. The creation of a DNA double strand break at the HO cut site by induction of the HO endonuclease in vivo caused one nucleus to arrest while the other continued with DNA synthesis and nuclear division. This indicates that the signal for cell cycle arrest is not a component that can be easily transmitted from one nucleus to the other.

DNA stained heterokaryon with induced break