Molecular cytogenetics is a field of cytogenetics developing techniques, based on DNA sequence homologies, allowing the specific identification of all or part of one or more chromosomes.
Molecular cytogenetics which is a karyotype complementary technique based on in situ hybridization.
The principle is based on the use of a molecular probe, ie a small sequence of DNA (or RNA) whose normal location is known in the genome and which is chemically labeled to can be identified later. This probe is brought into contact with the chromosomes of a mitosis (or interphase nuclei) and will hybridize (bind) specifically at the level of its complementary sequence. The probe can then be viewed under a microscope whose location precisely identifies the chromosomal region of which it is complementary.
The probes used for the in situ hybridization identify either repeated sequences (long arm of the Y, specific or non-specific centromeric alphoid probes, non-specific telomeric probes), or unique sequences (locus or regional probes), or a mixture of unique sequences hybridizing on all or part of a chromosome (total or partial paint probes).