AcroM fluorescent in situ hybridization analyses of marker chromosomes

The presence of a de novo supernumerary marker chromosome (SMC) poses probl ems in genetic counseling. The consequences of the additional chromosomal m aterial may range from harmless to detrimental. As the composition of a SMC cannot be deciphered by traditional banding analysis, sophisticated method s are needed for their rapid and detailed analyses. A new strategy is prese nted, which allows the elucidation of the composition of SMCs in one or two hybridizations. One hybridization, termed AcroM-FISH, involves a newly gen erated probe mix, which consists of painting probes for all acrocentric chr omosomes, centromere probes for chromosomes 13/21, 14/22, 15, and a probe s pecific for rDNA, each labeled with a specific combination of fluorochromes . This probe mix is sufficient to characterize approximately 80% of all SMC s. For the other 20% of SMCs, chromosomes can be analyzed in a second hybri dization by multicolor karyotyping, for example, multiplex FISH (M-FISH), t o check for the presence of cuchromatin of other chromosomes. The potential of AcroM-FISH was tested in various applications.