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Is It All a Question of Size?
a University Women's Hospital/Department of Research, Basel, Switzerland b Department of Obstetrics and Gynecology, University of Bari, Bari, Italy c Division of Haematology II, University of Bari, Bari, Italy
Key Words: circulatory DNA • prenatal diagnosis • electrophoresis • size fractionation
Address for correspondence: Sinuhe Hahn, Laboratory for Prenatal Medicine, Department of Research, University Women's Hospital, Spitalstrasse 21, CH 4031 Basel, Switzerland. Voice: +41-61-265-9224; fax: +41-61-265-9399. e-mail: shahn{at}uhbs.ch
Fetal cell-free DNA (cf-DNA) represents only a small fraction of the total cf-DNA in maternal plasma. This feature has rendered it difficult to reliably distinguish fetal alleles which are not very disparate from maternal ones, such as those involving point mutations, by conventional polymerase chain reaction (PCR)-based approaches. It has recently been shown that cell-free fetal DNA molecules have a smaller size than comparable cf-DNA molecules of maternal origin, and that this feature can be exploited for the selective enrichment of fetal DNA sequences, thereby permitting the detection of otherwise masked fetal genetic traits. By the use of this approach, we have shown that it is possible to detect fetal genetic loci for microsatellite markers, as well as point mutations involved in disorders such as achondroplasia and
 -thalassemia.
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