Fig.1 Isolation of E.coli extracts containing plasmid pTaq1. (a) Plasmid concentration (ng/μl) and purity (260/280) were determined by spectrophotometry. D refers to culture prepared by demonstrator and S refers to culture prepared by students. (b) Gel electrophoresis of plasmid pTaq1 purified by small-scale alkaline extraction (mini-prep) from E.coli cultured on L-broth containing carbenicillin. 1kb is the DNA molecular weight ladder. Band1, plasmid multimer. Band2, open circular plasmid. Band3, supercoiled plasmid. Band4, RNA residue.