High-resolution chromosome R-banding in lymphoblastoid cell lines by the combined use of cell synchronization and ethidium bromide treatment.

A reliable method for obtaining high-resolution R-banded chromosomes from lymphoblastoid cell lines is described. The cell cultures are subjected to S-phase synchronization in the presence of excess thymidine (300 micrograms/ml) for 17 to 19 hr, followed by BrdU treatment (30 micrograms/ml) for 6.5 hr. Prior to harvest, they are exposed to ethidium bromide (7.5 micrograms/ml) for 1.5 hr and Colcemid (0.02 microgram/ml) for 30 min. Using this method, high-resolution R-banded chromosomes at the 550-850 band level were obtained with frequencies as high as 70% of all mitotic cells.