A feature of each individual genome
is that the length of the fragments of DNA cut with restriction enzymes (a class of endonucleases that recognizes specific sequences of nucleotides) is unique. The technique of Restriction Fragment Length Polymorphism (RFLP)
exploits this singularity by comparing the enzyme restrictions of different
DNAs by gel electrophoresis.
Based on the principles of the
RFLP, some variations of the technique have been developed: the Terminal Restriction Fragment Length Polymorphism (TRFLP) compares the differences in the position of restriction sites of ribosomal genes. Another example is the
Amplified Fragment Length Polymorphism (AFLP), which combines restriction with
the PCR technique and uses primers containing the sequences of nucleotides of
specific restriction sites. Finally, when the differences in the restriction
fragment lengths are tested in the amplicons produced by the PCR the technique
is named CAPS: Cleaved Amplified Polymorphic Sequences.