Analysis of hcDNA with DNaseI. hcDNA was 5'-end-labelled at the Eco RI site and fractionated on a preparative 8% polyacrylamide gel as shown on the left on the Figure. Material from each gel slice was eluted, digested with DNase I, and analyzed on a denaturing polyacrylamide-urea gel. For each sample a control, labeled (-), was also loaded on the gel. Samples are: G+A: G+A sequencing reaction as a size marker; ds: double strand in the regular B-form conformation; 1–5: hcDNA, slices 1 to 5 of the preparative gel. Scans of the DNase-digested samples are shown.