Melting DNA becomes barcode

New DNA test method uses different melting point of the base pairs

Test chamber for the new DNA test: The DNA is filled in, drawn out, heated and read out in one operation. © Lund University
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A completely new method to represent the individual DNA sequence of genes has now been developed by Swedish researchers. The "barcode" method exploits the fact that the different base-pair combinations of the DNA melt at different temperatures. A single DNA molecule is enough for the test, as the scientists report in the journal "Proceedings of the National Academy of Sciences". Therefore, for example, pathological gene changes can be detected faster and far less costly than before.

For current genetic testing, the DNA is first amplified after isolation from blood or tissue samples. Only after this several hours long procedure, the actual evaluation can begin. But a new method, now developed by researchers at Lund University, makes this time-consuming replication obsolete. "The technology is faster, simpler and cheaper than existing methods, " explains Jonas Tegenfeldt, a solid-state physicist at Lund University. "Therefore, we hope that it can be used in hospitals in the future as routine."

Melting temperature different

The new technique is based on the fact that the base pairs, which form the code of the DNA molecule, melt at different temperatures. For example, the bases guanine (G) and cytosine (C) are more strongly bound together and therefore melt much later than adenine (A) and thymine (T). In a first step, the scientists stain the chromosomes with a fluorescent dye. Then the DNA is filled into specially constructed nanocubes and stretched from their normal, helical spiral form into a stretched out form.

Chromosome with band pattern

Next, the stretched molecule is deliberately heated so that only the AT mating melts. The melting takes away the luminosity of the dye, so that the molten areas of the DNA become clearly visible as darker bands. In principle, the entire chromosome appears as a barcode of dark and light bands. This "barcode" view is nothing new per se, but the fact that with the new method, it has been available after just over an hour rather than 24 hours at least. The usually time-consuming DNA tests can therefore be extremely shortened. Also enzymatic transformations of the DNA are not necessary here.

Procedure of the procedure Lund University

No replication, only one molecule

Another advantage of DNA melting is that only one DNA molecule is needed, and time-consuming replications are completely eliminated. As a result, even tiny sample volumes or several different cells can be compared very easily and quickly. Although the barcode is not precise enough to read the entire genome base for base, it gives a thousandfold better insight into the gene sequence than previous barcode methods. It could also be suitable as a starting point for more precise analyzes. display

Use as a rapid test in the hospital

For example, Tegenfeldt sees applications as a quick analysis in the hospital: "The barcode technique could be an easy way to determine what types of viruses and bacteria we have in front of us, " the researcher explains. "But we can also find out if something in the human genome is wrong, because we can see if any part of the chromosome has shifted, for example. This happens with certain illnesses. "So, whether someone has the predisposition to a disease could be recognized more easily in the future. But even in criminalistics, the new rapid test could serve well.

(Lund University, 20.07.2010 - NPO)