(APS) were obtained from Sigma (St. Louis, MO). 20-Deoxyadenosine-
50-O-(1-thiotriphosphate) sodium salt (dATP-a-S) was
purchased from Amersham Pharmacia Biotech (Amersham, UK).
dGTP, dTTP, dCTP were purchased from Amersham Pharmacia
Biotech (Piscataway, NJ). Other solutions were prepared with
deionised and sterilised H2O.