Restriction fragment length polymorphism to detect sickle-cell anemia.

The normal allele has a GAG sequence recognized by the MstII restriction enzyme, produces 2 fragments on a Southern blot, while the mutant βs allele contains a GTG sequence resulting in a single large fragment.

In this pedigree, II-1 is homozygous normal, II-2 is homozygous recessive, and II-3 is a heterozygous carrier.