It is nearly impossible to determine the origin of small supernumerary marker chromosomes (SMCs) by routine cytogenetics. However, fluorescence in situ hybridization (FISH) methods are highly suited for that purpose. Twenty-four-color FISH approaches using whole chromosome painting probes can be used successfully for the determination of such markers' chromosomal origin if the SMC is larger than 17p. Therefore smaller SMCs found in clinical cytogenetics in 0.01-0.05% of cases often could not be characterized in the past. The one-step characterization of small SMCs became possible by recently established methods such as centromere-specific multicolor FISH (cenM-FISH) and related probe sets.


In about 50% of cases with small SMCs, the derivatives are known to originate from chromosome 15.[1] Among the remaining cases, there is: 1) a great variation in chromosomal and parental origin; 2) a possibility of genomic imprinting effects; and 3) homozygosity of autosomal recessively inherited mutations in uniparental isodisomy.[1,2] As great dissimilarities in their clinical outcomes are reported, too, the characterization of prenatally detected—particularly de novo—SMCs is of significant interest for more appropriate medical care and genetic counseling. Characterization of one or more SMCs in a patient should be followed by testing for uniparental disomy (UPD), as UPD can cause clinical signs and symptoms, as well.[3-5]

Was this article helpful?

0 0
Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

Get My Free Ebook

Post a comment