The mapping of YAC 964c10 (red) and cosmid D12Z3 (green) to a leukemia cell. The latter is a centromere probe for chromosome 12. The normal and rearranged chromosome 12 are indicated by an arrowhead and a large arrow, respectively. der(15) chromosome is identified with a short arrow. YAC 964c10 hybridized to the normal chromosome 12 and der(12) as well as to the der(15) chromosome. Signals on the der(12) are smaller than those on the other chromosomes