Since no 3' OH is available for the next nucleotide to attach, the chain terminates. If a mixture of dideoxy and deoxy nucleotides is provided, a nested set of fragments is produced, each terminated by one of the 4 dideoxynucleotides and varying in size by a single nucleotide. It is only necessary to separate the fragments by size and to determine which dideoxynucleotide is attached to the end to be able to reconstruct the sequence. In an automated sequencer each of the 4 dideoxy nucleotides is labeled with a separate dye. Thus all four sequence reactions can be run in a single lane or capillary.
AFLP analysis has many uses in molecular biology genetics and systematics.
Under ideal conditions it is a reproducible and reliable technique. However, as in any other technique, unexpected results may occur in some cases. A. Human DNA was being analyzed and selective primers with only one selective nucleotide instead of the normal three were used for the final amplification. Digestion of human DNA with a restriction enzyme produces a very large number of fragments. If only one selective nucleotide were used, too many fragments would be produced to be resolved on a gel.