- based ▁size ▁selection . ▁ ▁Att aching ▁adapter ▁sequences ▁ ▁Ad apter ▁DNA ▁sequences ▁must ▁be ▁attached ▁to ▁the ▁unknown ▁DNA ▁fragment ▁so ▁that ▁DNA ▁segments ▁with ▁known ▁sequences ▁fl ank ▁the ▁unknown ▁DNA . ▁ ▁In ▁the ▁first ▁round ▁of ▁adapter ▁lig ation , ▁right ▁( Ad 1 5 3 _ right ) ▁and ▁left ▁( Ad 1 5 3 _ left ) ▁ad ap ters ▁are ▁attached ▁to ▁the ▁right ▁and ▁left ▁fl anks ▁of ▁the ▁fragment ed ▁DNA , ▁and ▁the ▁DNA ▁is ▁ampl ified ▁by ▁PC R . ▁A ▁spl int ▁o lig o ▁then ▁hy brid izes ▁to ▁the ▁ends ▁of ▁the ▁fragments ▁which ▁are ▁lig ated ▁to ▁form ▁a ▁circle . ▁An ▁ex on uc lease ▁is ▁added ▁to ▁remove ▁all ▁remaining ▁single - str and ed ▁and ▁double - str and ed ▁DNA ▁products . ▁The ▁result ▁is ▁a ▁completed ▁circular ▁DNA ▁template . ▁ ▁Rol ling ▁circle ▁rep lication ▁ ▁Once ▁a ▁single - str and ed ▁circular ▁DNA ▁template ▁is ▁created , ▁containing ▁sample ▁DNA ▁that ▁is ▁lig ated ▁to ▁two ▁unique ▁adapter ▁sequences ▁has ▁been ▁generated , ▁the ▁full ▁sequence ▁is ▁ampl ified ▁into ▁a ▁long ▁string ▁of ▁DNA . ▁ ▁This ▁is ▁accomplished ▁by ▁rolling ▁circle ▁rep lication ▁with ▁the ▁Ph i ▁ 2 9 ▁DNA ▁polym er ase ▁which ▁bind s ▁and ▁rep licates ▁the ▁DNA ▁template . ▁ ▁The ▁newly ▁synth es ized ▁str and ▁is ▁released ▁from ▁the ▁circular ▁template , ▁resulting ▁in ▁a ▁long ▁single - str