Identification of flow-sorted chromosomes by G-banding and in situ hybridization.

The identification of flow-sorted chromosomes is a very important tool for checking the purity of the fractions obtained. An easy and reproducible method for obtaining G-banded chromosomes with good resolution of bands is described. Also, we are able to show that the percentage of chromosomes which can be clearly distinguished by this procedure depends to a large extent on the duration of mitotic arrest. In particular when sorting chromosomes from human-rodent hybrid cell lines, the possibility of using in situ hybridization in addition to conventional staining techniques to characterize the chromosomes can help overcome the problem of highly condensed chromosomes and chromosomal fragments of unknown origin, which cannot be identified otherwise. Thus, we have developed an in situ hybridization technique, based on biotin-labelled human genomic DNA, which allows a clear distinction between human and rodent chromosomal material to be made.