Gene mapping by chromosome spot hybridization

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Abstract
A method is described for the localization of cloned single‐copy genes to flow‐sorted chromosomes. Chromosomes were sorted directly onto nitrocellulose filters and the chromosomal DNA was subsequently hybridized with gene‐specific radioactively labeled DNA probes. Mild aspiration of the filters during sorting was applied to collect the deflected chromosomes in a small spot. Sorting of 10,000–30,000 chromosomes was sufficient to detect gene‐specific hybridization with single‐copy DNA probes. Using this technique, we have sublocalized the human c‐myb oncogene to 6q21–q23 by sorting translocated chromosomes with breakpoints in the q21 and q23 region of chromosome 6. Chromosome spot hybridization appears to be a rapid and simple method to assign cloned genes to chromosomes. Hybridization of an unlocalized gene probe to spots of chromosomes pre‐enriched by velocity sedimentation can quickly narrow the choice of chromosomes which need to be sorted. Conversely, individual chromosomes in a flow karyotype can be identified by hybridizing sorted chromosomal DNA with chromosome‐specific DNA probes.