ABSTRACT
Plasmids are extrachromosomal molecules of deoxyribonucleic acid (DNA) that are capable of autonomous replication. They are found in many bacterial genera. The bacterial cells are treated with alkaline sodium dodecyl sulfate (SDS). SDS is a detergent that partially lyses the cell membrane producing small "holes" which allow plasmid DNA to be released while retaining much of the high molecular weight chromosomal DNA. This chapter describes three mini-prep methods: alkaline lysis method of H. C. Birnboim and J. Doly; method of C. I. Kado and S. T. Liu; and Brij lysis method. It discusses how the methods may be adapted to permit digestion of plasmids with restriction endonucleases. This is useful for comparing plasmids of similar sizes or those which encode similar characteristics. The chapter provides details of agarose gel electrophoresis. In the technique of agarose gel electrophoresis, plasmids are separated on the basis of molecular size.
