Gel electrophoresis of PCR-amplified DNA testing the specificity of the A and B1 primers. PCR products were amplified using P1 and A as primers from 0B total plant DNA (lanes 1 and 3), 2B total plant DNA (lanes 5 and 7), clones derived from 0B total plant DNA (lanes 9 and 11), and clones derived from microdissected B chromosome DNA (lanes 13 and 15) and using P1 and B1 as primers from 0B total plant DNA (lanes 2 and 4), 2B total plant DNA (lanes 6 and 8), clones derived from 0B total plant DNA (lanes 10 and12), and clones derived from microdissected B chromosome DNA (lanes 14 and 16). Fragment sizes are indicated in base pairs.