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Genome Structure and Replication

Walton L. Fangman, Virginia A. Zakian


Saccharomyces cerevisiae is an ideal model system for studies on the structure and replication of the eukaryotic chromosome. Yeast cells are easy to grow and handle biochemically, and they are amenable to sophisticated genetic manipulations. The availability of mutants is especially critical for a detailed understanding of the replication process. Without them it is almost impossible to determine the in vivo role of a particular protein. Although the small size of yeast chromosomes makes cytological studies difficult, it provides the possibility of isolating intact the DNA corresponding to a given chromosome. Moreover, chromosomal substructures such as telomeres and centromeres are found in far higher concentrations in yeast DNA than in that of higher eukaryotes and can therefore be studied with greater ease. The small genome and low percentage of repetitive sequences has enabled the relatively rapid isolation and characterization of specific sequences by recombinant DNA technology. The ability to transform yeast with recombinant DNA plasmids is invaluable for investigating the functions of specific DNA sequences, including those involved in replication. Finally, yeast contains an endogenous multiple-copy extrachromosomal plasmid called 2-micron (μ) DNA, which provides a tractable model for some features of chromosomal DNA replication.

In this paper we have attempted to provide an overview of chromosomal organization and DNA replication. More detailed information on the following topics can be found in other papers in this volume: Mitochondrial Genetics and Function (Dujon); The Yeast Plasmid 2μ Circle (Broach); The Saccharomyces cerevisiae Cell Cycle (Pringle and Hartwell). Information on the structures...

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