Optimal conditions for supercoil DNA sequencing with the Escherichia coli DNA polymerase I large fragment.

Sequencing ladders produced from supercoiled DNA templates with the Escherichia coli DNA polymerase Klenow fragment are often unreadable because of a high background and misincorporated nucleotides. This study showed that contaminating RNA molecules can interfere with template:primer hybridization. Procedures are provided for the purification of template DNA and stringent conditions for primer-template hybridization that overcome these problems.