1. Dilute 1 Ál of the sample 1:100 in 0.2 M EDTA (pH 8.0).
2. In duplicate, spot 3 Ál of the diluted sample on Whatman DE 81 circular filters.
3. Dry the filters briefly under a heat lamp. One filter will be used
directly for the determination of total cpm in the sample.
4. Wash the other filter in 50 ml of 0.5 M sodium phosphate (pH 6.8)
for 5 minutes to remove the unincorporated dNTPs.
5. Repeat wash for 5 minutes.
6. Dry the washed filter under a heat lamp.
7. Add the appropriate amount of scintillation fluid to each filter and
count in a scintillation counter.