Under the Microscope: Samples Required For DNA Testing - To The Bone!
Amplification techniques, such as polymerase chain reaction (PCR), etc., now allow minute samples to be tested, the larger the sample, the better the chance of a suc c essful DNA test. Post-mortem material is inferior to live blood and tissue for DNA fingerprinting if any significant post-mortem change has proceeded enough to break down nuclear chro m atin. Plain blood samples should be taken, however, though leucocytes may have already disintegrated. Some 5 ml of blood is taken into an EDTA tube, which extracts metallic ions and not only prevents clotting, but inhibits enzymes in blood or micro-organisms, which may break down DNA during storage. The best material is said to be - muscle or the spleen and, if decomposition is advancing, the bone marrow is recommended. At least 0.5 g of tissue should be cut from the parenchyma of an organ and placed in a small plastic tube with no fixative or preservative. This should be frozen at -20°C if there is likely to be...