Radiation-Induced Mouse Leukemia: Consistent Occurrence of an Extra and a Marker Chromosome

Granulocytic leukemia, induced in the primary mouse by x-irradiation, was serially transmitted to RF/Up mice. An extra chromosome, as well as a morphologicaly unusual chromosome, was found in the bone marrow cells of all the leukemic mice that had been injected previously either with leukemic spleen cells or with cell-free ultracentrifugates. This suggests that the changes in the chromosomes are caused by a virus.