ASO analysis is only one of the methods used to detect genetic polymorphisms. Direct DNA sequencing is used to initially characterize the mutation, but is too laborious for routine screening. An earlier method, Restriction Fragment Length Polymorphism (RFLP) didn't need to know the sequence change beforehand, but required that the mutation affect the cleavage site of a Restriction Enzyme. The RFLP assay was briefly adapted to the use of oligonucleotide probes, but this technique was quickly supplanted by ASO analysis of polymerase chain reaction (PCR) amplified DNA. The PCR technique itself has been adapted to detect polymorphisms, as allele-specific PCR. However, the simplicity and versatility of the combined PCR/ASO method has led to its continued use, including with non-radioactive labels, and in a "reverse dot blot" format where the ASO probes are bound to the membrane and the amplified sample DNA is used for hybridization.