Analysing and sorting human chromosomes

SUMMARY Analysing and sorting human chromosomes by flow cytometry is a powerful tool in the hands of the molecular biologist. Because of the large number of chromosomes analysed by flow, typically 105 for each sample, estimates of the distribution of DNA throughout the chromosome complement of an individual can be made to within three megabase pairs. Rearrangements of DNA in this size range can often be clearly seen and measured by flow cytometry in situations where it was not obvious by traditional cytogenetics. The production of enriched samples of a particular chromosome by flow sorting and the subsequent construction of DNA libraries has played an important part in mapping genes to particular hereditary diseases. Techniques now exist which allow the hybridization of a few thousand sorted chromosomes with characterized or uncharacterized DNA probes to give relatively quick answers about specific chromosome genes. The process of obtaining a sorted chromosome sample from a growing population of peripheral blood lymphocytes or lymphoblastoid cells is compared with other methods of achieving similar results in molecular biological terms. Advances in flow cytometric techniques, which include slit‐scanning and hybridization of DNA probes in suspension, are likely to improve the enrichment quality of specific sorted human chromosomes.