Methods for constructing consecutively connected copies of nucleic acid molecules are disclosed. Consecutively connected copies of nucleic acid molecules can be used to perform sequencing of the same nucleic acid molecules several times, improving overall accuracy of sequencing. Connected copies of nucleic acid molecules can be constructed by circularizing nucleic acid molecules, performing rolling circle amplification and debranching with nicking and polymerases comprising 5′-3′ exonuclease and/or flap endonuclease activity.