Synthetic allele-specific oligonucleotides (ASOs) can identify alleles that differ by a single nucleotide, such as the sickle-cell trait.

The β-globin gene is amplified by PCR and denatured, then hybridized to radioactive ASO probes on filters for autoradiography.

This ASO is made from the normal (A) β-globin allele (containing a GAG codon); AA-homozygous individuals show heavy hybridization; AS-heterozygous individuals show weaker hybridization; and SS sickle-cell individuals show no hybridization. Continue