Below on the left is a diagram of double-stranded dna of a circular plasmid from a bacterial cell. the positions x, y, and z are sites where the plasmid dna is cleaved by restriction enzymes x, y, and z, respectively. the numbers are the size in kilobase pairs (kb) of the dna regions between the restriction sites. on the right is a diagram of an electrophoresis gel. lane 1 is the ladder, comprised of dna fragments that range in size from 1–12 kb showing the position of each band size after electrophoresis. the other lanes are dna bands observed from digestion of the plasmid with one of more of the restriction enzymes.