Rapid mapping and subcloning of genomic clones in bacteriophage lambda by PCR.

Burkitt’s lymphoma-derived cell line, Raji, showed a cloning efficiency of 50%). These results are comparable to the lowest seeding regime used in this experiment and suggest that the medium used substantially affects clonal growth. Thus, the combination of an enriched medium and seeding the B cells directly onto a growing feeder layer clearly results in an improvement in cloning efficiency. This method is particularly useful when the number of transfectants is very low because it is unlikely that single positive wells will have arisen from more than one cell. This is borne out by the successful cloning of single cells (from a population of 2–4 × 104 cells per well) after transfection with YAC DNA (unpublished observations). In these instances, the number of positive cells was often <1 in 2 × 106 starting cells.