DNA system provided the first clear suggestion that DNA carries genetic information. In 1933, while studying virgin sea urchin eggs, Jean Brachet suggested that DNA is found in the cell nucleus and that RNA is present exclusively in the cytoplasm. At the time, "yeast nucleic acid" (RNA) was thought to occur only in plants, while "thymus nucleic acid" (DNA) only in animals. The latter was thought to be a tetramer, with the function of buffering cellular pH. In 1937, William Astbury produced the first X-ray diffraction patterns that showed that DNA had a regular structure. In 1943, Oswald Avery, along with
Cell-free fetal DNA pregnancies complicated by preeclampsia have significantly higher levels of cffDNA that those in normal pregnancies. This holds true for early onset preeclampsia. New generation sequencing may be used to yield a whole genome sequence from cffDNA. This raises ethical questions. However, the utility of the procedure may increase as clear associations between specific genetic variants and disease states are discovered. Cell-free fetal DNA Cell-free fetal DNA (cffDNA) is fetal DNA which circulates freely in the maternal blood. Maternal blood is sampled by venipuncture. Analysis of cffDNA is a method of non-invasive prenatal diagnosis frequently ordered for pregnant women of advanced