Molecular cytogenetics involves the combination of
molecular biology and
cytogenetics. In general this involves the use of a series of techniques referred to as
fluorescence in situ hybridization, or FISH, in which
DNA probes are labeled with different colored fluorescent tags to visualize one or more specific regions of the genome. FISH can either be performed as a direct approach to metaphase chromosomes or interphase nuclei. Alternatively, an indirect approach can be taken in which the entire genome can be assessed for copy number changes using virtual karyotyping.
Virtual karyotypes are generated from arrays made of thousands to millions of probes, and computational tools are used to recreate the genome
in silico.