Many techniques exist for testing whether a sample of DNA carries a mutation. In this animation, we explore the use of two different techniques for identifying whether an individual carries the sickle-cell allele of the β-globin gene. One procedure is called allele-specific oligonucleotide hybridization (ASO). In ASO, the binding of a probe to sample DNA indicates that a particular allele is present in the DNA. The other procedure, DNA testing by allele-specific cleavage, uses restriction enzyme