Process for producing biologically functional molecular chimeras

A method for replicating a biologically functional DNA, which comprises:

• transforming under transforming conditions compatible unicellular organisms with biologically functional DNA to form transformants;
• said biologically functional DNA prepared in vitro by the method of:
• (a) cleaving a viral or circular plasmid DNA compatible with said unicellular organism to provide a first linear segment having an intact replicon and termini of a predetermined character;
• (b) combining said first linear segment with a second linear DNA segment, having at least one intact gene and foreign to said unicellular organism and having termini ligatable to said termini of said first linear segment, wherein at least one of said first and second linear DNA segments has a gene for a phenotypical trait, under joining conditions where the termini of said first and second segments join to provide a functional DNA capable of replication and transcription in said unicellular organism;
• growing said unicellular organisms under appropriate nutrient conditions;
• and
• isolating said transformants from parent unicellular organisms by means of said phenotypical trait imparted by said biologically functional DNA.