Current techniques in chromosome analysis.

New techniques in chromosome analysis provide more precision in the identification of chromosomal abnormalities than was previously possible. Specific small chromosome changes can now often be related to defined syndromes of mental retardation and congenital anomalies, or to malignant disease. Some aspects of chromosomal function can also be investigated cytologically, e.g., abnormalities in DNA repair, susceptibility to damaging agents, DNA replication sequences, and sites of inactive heterochromatin and of actively transcribing ribosomal DNA. Future trends will involve even finer resolution of the chromosomal bands, using both extended chromosomes and probes specific for small chromosomal regions, as well as continued localization of specific genes on the cytologic map.