R. sphaeroides DNA containing the gene of interest

R. sphaeroides cut ends of DNA

pK19 DNA

Note the complementarity of the "sticky ends" of the pK19 and the R. sphaeroides DNA.

Cool, add DNA ligase and the molecules can reanneal. Resulting in a variety of recombinant forms.

The one of interest is the plasmid containing the R. sphaeroides DNA.