Fig. 3.

Protocols of gpt delta transgenic mouse gene mutation assay.

Two E. coli host cells are infected with the rescued lambda EG10 phages. One is E. coli YG6020 expressing Cre recombinase for 6-TG selection and the other is P2 lysogen for Spi⁻ selection. In E. coli YG6020, lambda EG10 is converted to the multi-copy-number plasmid pYG142 carrying gpt and CAT. E. coli cells harboring plasmid carrying mutant gpt can form colonies on the plates containing chloramphenicol and 6-TG (gpt selection). Mutant lambda phage lacking the functions of red and gam can form Spi⁻ plaques on plates containing P2 lysogen (Spi⁻ selection).