purified protein p2 of phage phi 29 , characterized as a specific dna polymerase involved in the initiation and elongation of phi 29 dna replication , contains a 3 ' -- -- 5 ' exonuclease active on single-stranded dna , but not on double-stranded dna .
C0012935
single-stranded dna
C0012854
double-stranded