A method is provided for generating single-stranded DNA circles from a biological sample. The method comprises the steps of: treating the biological sample with an extractant to release nucleic acids, thereby forming a sample mixture neutralizing the extractant denaturing the released nucleic acids to generate single-stranded nucleic acids and contacting the single-stranded nucleic acids with a ligase that is capable of template-independent, intramolecular ligation of single-stranded DNA to generate the single-stranded DNA circles. All the steps of the method are performed without any intermediate nucleic acid isolation or nucleic acid purification. The single-stranded DNA circles may be amplified and further analyzed. Also provided is a kit which comprises compositions for carrying out the novel methods.
