Figure 1. Schematic view of Maxam–Gilbert reaction products. G, A, R, Y and C represent the specific chemical reactions that identify the relative positions of guanine (G), adenine (A), purine (‘R’; G and A), pyrimidine (‘Y’; C and T) and cytosine (C) bases, respectively. In this example the fragment is labelled at the 5¢ end. Reading from the bottom towards the top of the gel, the banding pattern corresponds to the sequence 5¢ GGTACGCCTGA 3¢.

Figure 2. Data produced using Sanger sequencing reaction. G, A, T and C represent the sequencing reaction products resulting from inclusion of ddGTP, ddATP, ddTTP or ddCTP. Since enzymatic synthesis proceeds 5¢ to 3¢, the smaller fragments identify bases that are closer to the primer (5¢ end of the sequence information). (a) Schematic view of Sanger reaction products. The DNA sequence identified by this pattern of bands is indicated. (b) Photograph of corresponding sequence data.

Figure 3. (a) Raw sequence data collected on an automated DNA sequencer (Perkin-Elmer ABI PRISM Model 377). The four colours indicate the relative position of the bases in the DNA fragment. Each four-colour vertical line corresponds to a different sequence reaction. The smaller fragments (nearer the cathode) identify bases that are closer to the primer (5¢ end of the sequence information). (b) Portions of a representative, analysed sequence determined by the automated sequencer.