Centromerespecific Fish Approaches

To characterize an SMC, whole chromosome painting FISH approaches such as multiplex FISH (M-FISH) or spectral karyotyping (SKY) (overview in Refs. [6] and [7]) are well suited as long as the marker is larger than the short arm of chromosome 17. If it is smaller and including only small chromosome fragments with no euchromatin or nearly no euchromatin, then often no result may be obtained (e.g., Ref. [8]).

For the rapid characterization of such small SMCs, a multicolor FISH technique was established, allowing the unambiguous one-step identification of all human centromeric regions, excluding nos. 13 and 21. The so-called cenM-FISH[9] (Fig. 1) is based on all available centromere-specific DNA probes, labeled in five different fluorochromes. A comparable multicolor FISH, called centromeric multiplex FISH (CM-FISH) approach, was published in parallel.[10]

SMCs are initially detected during GTG banding analysis and can be characterized for the presence of an acrocentric chromosome-derived short arm by nucleolus organizing region (NOR) staining. According to the NOR staining result (NOR-negative or NOR-positive), the origin of SMCs can be determined by application of all human centromeres in one experiment (i.e., cenM-FISH,[9]) or by the acrocentric centromere-specific multicolor FISH (acro-cenM-FISH) probe set,[11] respectively. The latter consists of a probe specific for the acrocentric human p-arms, a NOR-specific probe, a probe specific for Yq12, and all centromere-specific probes for 13/21, 14/22, 15, and 22.[11] These two approaches were successfully applied in about 100 cases with SMCs up to present[9,12-15] (SMC-homepage: http://mti-n.mti. uni-jena.de/-huwww/MOL_ZYTO/sSMC.htm).

In general, neocentromeric SMCs are not stained by any of the two aforementioned approaches; in this case, other techniques for their characterization, such as M-FISH (overview in Refs. [6] and [7]), microdissection of SMCs (e.g., Ref. [16]), or micro-CGH,[16] have to be performed. About 60 cases with neocentromeres are reported in the literature (for review, see Ref. [17]).

After determination of the origin of a small SMC with centromeric DNA, the most important question to address is if there is euchromatic material of the corresponding chromosome on it, or not. This question for partial trisomy can be studied by hybridizing whole chromosome painting or chromosome arm-specific probes (e.g., Ref. [8]). Another possibility is the use of probes, which are able to subclassify chromosomal regions such as multicolor banding (MCB) (e.g., Ref. [16]; Fig. 2). Recently, a probe set specific for the pericentric region of all human


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.

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