In situ hybridization analysis of isodicentric X-chromosomes with short arm fusion

We present here an alternative approach to the study of mosaic cell lines containing dicentric chromosomes. The approach is based on chromosome-specific non-radioactive in situ hybridization with centromere (alpha satellite DNA) probes. The hybridization analysis may be used as an alternative to the C-band analysis, while at the same time to some extent replacing the Q-band analysis as well. The advantage of using in situ hybridization is mainly that it allows the very fast screening of a large number of metaphases. We illustrate this new application of the technique by using it for the analysis of two cases of isodicentric X-chromosomes. The approach is expected to be generally applicable, so that it may be applied to the scoring of other types of chromosomal mosaicism as well.