| Abstract |
Cytogenetic studies were performed on an established cell line, OK,
derived from the kidney tissue of Didelphys virginiana, the North American
opossum (2n = 24). This line was shown to have a modal number of 23, and a
considerable degree of aneuploidy. Karyotypes exhibited 11 sets of
pairable chromosomes and one nearly metacentric, marker chromosome.
Studies on fluorescent stained interphase cells revealed the sex chromatin
body. The presence of 2 condensed bodies frequently seen in this study
supports the idea that there is no typical inactivation of one entire X
chromosome in the opossum and may represent another method of dosage
compensation in marsupials. The C-banding pattern revealed the exclusive
localization of constitutive heterochromatin within the sex chromosomes.
G-banding patterns enabled clear identification of all of the OK chromosomes.
The large, nearly metacentric, marker chromosome is shown to be the result
of the fusion of two telocentric chromosomes. Q-banding methods, while
producing some degree of longitudinal differentiation in the chromosomes,
did not give totally satisfactory results. Spontaneous SCE frequencies of
the OK chromosome is quite similar to the frequency of induced SCEs as a
result of exposure to 4 alkylating agents, (EMS, MMS, ENU, and MNU),
increased with increasing dose for all agents tested. The methyl
derivative of the alkane sulfonates and the methyl derivative of the
nitrosamides were more potent inducers of SCEs than their ethyl analogs.
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