Fill-in 

 condition
        
        10×fill-in buffer                 3(μL)
        20mM  DTT                     1.5
        0.5mM  dNTP                     3
        50μg/mL  BSA               1.5
        DNA                                  18
        H2O                                    2
        total                                   29

  method
     1°  solution(29μL)  →  37°C  water bath 5min
        2°  room temp. 5 min
        3°  add 1μL enzyme (Klenow:large fragement of E. coli polymerase I)
        4°  room temp. 30 min