Preparation of adapter-ligated amplicons

A method of preparing a sequencing library of a target DNA, comprising the steps of:

• (i) subjecting said target DNA to a PCR under conditions resulting in double-stranded PCR amplicons of said target DNA,
• (ii) contacting said double-stranded PCR amplicons with
• at least one polynucleotide kinase,
• at least one DNA ligase, and
• DNA adapter molecules,
• to obtain a reaction mixture, wherein the double-stranded amplicons are provided directly resulting from an amplification reaction without a subsequent chemical modification of the 3′ and/or 5′ termini, and
• (iii) incubating said reaction mixture under conditions simultaneously allowing
• a 5′ phosphorylation of said double-stranded PCR amplicons by said DNA ligase, and
• a joining of said DNA adapter molecules to at least one end of said double-stranded PCR amplicons by said DNA ligase,
• to obtain a sequencing library of said target DNA.