Figure 1.

For single-stranded library preparation, ancient DNA molecules are dephosphorylated and heat-denatured. A biotinylated adaptor oligonucleotide is ligated to 3′-ends of the molecules, which are immobilized on streptavidin-coated beads and copied by extension of a primer hybridized to the adaptor. One strand of a double-stranded adaptor is then ligated to the newly synthesized strand. Finally, the beads are destroyed by heat to release the library molecules (not shown).