The FISH technique requires viewing many cells to diminish artefactual problems in counting the painted chromosomes. FISH is good at identifying abnormal numbers of chromosomes such as trisomies and monosomies. FISH is also useful when probes are available for specific regions of chromosomes to determine if deletions, translocations, or duplications are present. In the above diagrams, a trisomy 21 is depicted at the right, while a probe for chromosome 22 has detected a translocation, probably to chromosome 9, on the left.