Unbalanced translocation, cosmid probe

A human metaphase from the amniotic fluid of a patient with an unbalanced translocation between chromosomes 4 and 9, t(4,9). The chromosomes have been highlighted with fluorescent probes that bind to specific sequences of DNA. The bcr cosmid (red) is present on both chromosome 9 homologues and also at the distal tip of the short arm of the der (4) - chromosome 4. Image by Dr John Crolla.