One and two codon insertion mutants of bacteriophage f1.

Simple methods for introducing one or two extra codons of genetic information into the f1 genome in vitro have been devised. The methods use various combinations of enzymes to insert three or six base-pairs into the RF1 DNA of the bacteriophage. Since such insertions do not cause frameshifts in coding regions, a number of these mutants are viable. Several such mutants were mapped and characterized. The methods described and variations of them can be applied to other circular DNA genomes.