Chromosomes and DNA of Microtus. III. Heterochromatin rearrangements in M. agrestis bone marrow clones.

Newborn Microtus agrestis were given single acute whole-body gamma-irradiation (350, 500, or 750R). C-banded bone marrow preparations showed cells with radiation-induced rearrangements of constitutive heterochromatin of the sex chromosomes, usually the consequence of single events, encompassing a wide spectrum of deletions and translocations. These cells persisted in bone marrow for more than a year after irradiation; however, many cells showing the same redistribution of heterochromatin constituted clones of both deletions and translocations. These results indicate that deletion or rearrangement of constitutive heterochromatin does not impair the capacity of bone marrow cells for further proliferation.