Science 44

Some bacteria contain a circular piece of DNA, known as a plasmid. This plasmid can be digested (cut open) by using specific enzymes known as restriction enzymes.

Once the plasmid is open, a gene can be attached and the plasmid closed to again form a circular piece of DNA, containing the foreign gene. This process is known as plasmid recombination.

Figure 1 shows a sequenced plasmid. Each colored arrow represents a known gene. Restriction enzymes will cut at recognition sites, certain nitrogenous base sequences.

Restriction enzyme sites are labeled, and restriction enzyme recognition sites were recorded and assigned a letter, a through. These data are recoded in Table 1.