we conclude that the poor ligation of taq i fragments of t4 and pbs1 dnas was due to the hydroxymethylation ( and glucosylation ) of cytosine residues at t4 's cohesive ends and the substitution of uracil residues for thymine residues adjacent to pbs1 's cohesive ends destabilizing the annealing of the restriction fragments .
C0041917
uracil
C0040087
thymine