Satellite DNA Organization in the Chromosomes of Primary Cells, L-Cells, and Sarcoma Mouse Cells 2

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Abstract
After one cell cycle in 5-bromodeoxyuridine (BUdR), the areas of repetitive DNA in the chromosomes of mice showed an asymmetrical distribution of the base analogue in the two chromatids. This phenomenon produced a differential Giemsa stain of the sister chromatids in the pericentromeric areas (TC-bands) that allowed the cytologic analysis of the organization of repetitive DNA. Primary cells, L-cells, and 180 ascites sarcoma cells from mice were grown for one cell cycle in BUdR. Some metaphase spreads were tested for C-banding; others were processed to induce TC-bands. DNA from primary and sarcoma cells was extracted and characterized by ultracentrifugation in CsCI gradients. Primary cells and L-cells showed C- and TC-bands in the centric regions of all chromosomes. Sarcoma cells had C-bands in all acrocentric chromosomes and in both arms of a metacentric marker chromosome. TC-bands appeared in about half the acrocentrics and in only one arm of the marker chromosome; the other arm and all the remaining acrocentrics lacked TC-bands. DNA characterization showed main and satellite bands with the same buoyant density in primary and sarcoma cells. The lack of correspondence between C- and TC-bands in sarcoma chromosomes may arise by changes in the molecular organization of the repetitive DNA or in the proteins associated with it. However, further investigations will be needed to clarify the problem.

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