Allele-specific oligonucleotides (ASOs)
synthesized from normal and mutant alleles and cloned by PCR
can screen for the Δ508 deletion in cystic fibrosis (CF).
DNA from the parents (I-1 and I-2) hybridizes to both ASOs, indicating that they are heterozygous.
DNA from II-1 hybridizes only to the Δ508 ASO, indicating that she is homozygous for the mutation and has CF.