Restriction fragment length polymorphism (RFLP)is able to sample about 5% of any gene. This technique was developed in the early 1980's and was the first method of genetic analysis available to molecular biologists. It was replaced by direct DNA sequencing.

Cutting a gene with a restriction enzyme allowed biologists to compare differences in the lengths of restriction fragments; DNA sequencing allowed biologists to read the exact order of nucleotide bases in the gene itself.