Chromosomes at the microscope

The past two decades have seen enormous progress towards understanding eukaryotic genes and genomes. Recombinant DNA technology has provided this power and hardly any contemporary experiment of gene structure and function is done today without recourse to methods of molecular biology. Considerable detail is known of the fine structure of genes and regulatory proteins that control not only single metabolic steps but even complicated developmental processes. It became obvious, however, that a gene can no longer be portrayed only one-dimensionally and that an understanding of the dimensions between the macromolecule DNA and the cytological entity chromosome, with its periodically recurring conformational changes, will be required. Yet the relationships between topographical, physical, and genetic distances of genes and their impact on genetic events, gene expression, and evolution have largely escaped analysis. It is therefore desirable to unravel chromosome structure and gene arrangement at the ultrastructural level. Modern high-resolution microscopes provide a powerful tool for studying such ultrastructural detail. For a more detailed introduction see the BMS homepage (http://www.wadsworth.org/ BMS/SCBlinks/mcewen/techniques.html) or the Compton Enciclopedia On-line (http://www.comptons.com/encyclopedia/ARTICLES/0100/01217280-A.html#P23A1).