Figure 1.

Schematic of the key steps employed in S1-seq: DNA from meiotic cells bearing processed Spo11 DSBs is embedded in agarose plugs to protect from shearing. Treatment with S1 nuclease and T4 DNA polymerase removes the 3′ overhang and prepares the ends for ligation with the 5′ biotinylated adaptor. Following extraction from the plugs and sonication, the biotinylated fragments are bound on streptavidin beads and the second adaptor is ligated. Low-cycle amplification by PCR creates the library that is submitted for next generation sequencing and eventually mapped to the reference genome.