ADVANCES IN THE PRENATAL AND MOLECULAR DIAGNOSIS OF THE HEMOGLOBINOPATHIES AND THALASSEMIAS

Prenatal diagnosis is available for pregnancies at risk for virtually all inherited disorders of hemoglobin production. The field of reproductive genetics must confront many ethical, legal, and social concerns regarding its use, many of which derive from a woman's desire to bear children but legal right to abortion. The goal of more widespread utilization of prenatal diagnosis is sought in the context of questioning the ethical control to be exerted over the biological makeup of future generations. Its appropriate application would be facilitated greatly by the availability of reliable DNA markers of disease severity. Advances in fetal sampling and in detecting mutant globin genes have provided the safe, accurate methodology required for prenatal diagnosis. Chorionic villus sampling in the first trimester has become standard practice, but second trimester amniocentesis also is used for sampling fetal DNA. The use of preimplantation diagnosis and testing fetal cells from the maternal circulation will soon be practical. DNA-based detection of globin gene mutations has been facilitated greatly by the polymerase chain reaction revolution, and several reliable diagnostic methods are available. Polymerase chain reaction-based methods rely on restriction analysis, allele-specific hybridization or amplification, DNA sequence analysis, and new non-polymerase chain reaction methods for DNA amplification in vitro. These methods are available for detecting hemoglobinopathy, thalassemia, and thalassemic-hemoglobinopathy genes that affect alpha- or beta-globin loci.