Rapid detection of human hemoglobin Quong Sze by polymerase chain reaction.

Human hemoglobin Quong Size is a nondeletional defect involving codon 125 of the alpha 2-globin gene. The molecular defect is a T to C mutation, therefore, a new MspI site (CCGG) is created. Using a pair of flanking DNA primers and polymerase chain reaction, a DNA fragment of 339 basepairs (bp) was amplified. After MspI restriction and gel electrophoresis, the mutation could be clearly identified by the presence of two fragments, 108 and 123 bp. This method is rapid and simple and will be very useful in the genetic counseling of Southeast Asians, including the Chinese, in which nondeletional alpha-thalassemia defects are common.