The NOR (Nucleolar Organizer Region) is located on every p-arm of the human acrocentric chromosomes. Enlargement of the acrocentric p-arms can be caused by an unusual variant or a translocation event. NOR stain of the p-arms is useful to detect such a p-arm variant. In the classification of small supernumerary marker chromosomes (SMCs) the Acro-P-Arms NOR FISH probe can detect the origin of DNA, in which about 80% will turn out to be derived from the acrocentric chromosomes. The Acro-P-Arms NOR FISH probe is optimized to detect the short (p) arm of all acrocentric human chromosomes. The probe is intended to be used on metaphase/interphase spreads.
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