Separation, digestion, and cloning of intact parasite chromosomes embedded in agarose

The chromosomes of most protozoan parasites cannot be visualized using conventional microscopy because they are too small and do not condense sufficiently at metaphase. Therefore, the development of pulsed field gel electrophoresis allowed the resolution of many parasite karyotypes for the first time. The ability to prepare intact chromosomes in agarose plugs and to isolate individual homologs by electrophoresis has led to many new applications in parasite genomic analysis. This chapter describes the preparation of chromosome plugs from single-celled protozoan parasites, providing numerous tips on how to achieve the highest-quality preparations that will last for years. We also provide detailed protocols for the manipulation of individual excised chromosomes, including restriction mapping and preparation of chromosome shotgun libraries as used in many of the genomic sequencing projects. The protocols provided here underpin several of the advanced methods of genomic analysis and manipulation described in this volume of parasite genomics protocols.