Sickle Cell Anemia: Prenatal Diagnosis
Restriction endonuclease analysis is now being used routinely in the prenatal diagnosis of hemoglobinopathies; in particular, accuracy in sickle cell disease is close to 100%. This is possible in the early fetus because the DNA defect is present in every cell, including fetal amniotic fluid celle (amniocytes) usually obtained between 16 and 20 weeks' gestation and fetal cells obtained by chorionic villus sampling at 8 to 12 weeks' gestation. The method involves the use of restriction endonudeases, bacterial enzymes that recognize and cleave specific DNA sequences. Today, about 200 such enzymes have been described and about 20 are commercially available. Their names come from the bacteria from which they were derived (eg, Hpal: Haemophilus parainfluenzae; BAMI: Bacillus amyeloliquefaciens). The other major technologic need is the identification of a specific complementary DNA (c-DNA) for the genomic area to be analyzed.
