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Einer der Tests, die Gminski und seine Mitarbeiter einsetzen, ist der sogenannte Komet-Test. Er zeigt, ob ein Luftschadstoffgemisch DNS-Brüche zur Folge haben kann. Die Wissenschaftler betten die Zellen dazu in Agarose, lösen ihre Membranen auf und setzen sie einem elektrischen Feld aus, der sogenannten Elektrophorese.
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One of the tests carried out by Gminski and his team is the so-called comet test which shows the researchers whether air pollutant mixtures lead to DNA breakage. This experiment involves placing the cells in agarose, dissolving their membranes and exposing the cells to an electrical field, a process known as electrophoresis. During electrophoretic separation, the negatively charged DNA migrates to the plus pole, during which the DNA fragments become separated from each other, and are rearranged according to their size. Smaller fragments can cover a longer distance in a given time than larger fragments. Damaged, fragmented DNA is able to leave the cell nucleus. Under the microscope, the damaged cells, which are stained with fluorescent dyes such as ethidium bromide, appear to have a tail of DNA fragments. "A cell, or rather its nucleus, once damaged by certain pollutants, looks like a comet," said Gminski. "Undamaged nuclei look like fluorescent spheres." In addition to the comet test, the scientists use another test to determine whether pollutants induce chromosomal damage in human lung cells. This test is known as a micronucleus test. The researchers also measure whether the emissions of the objects under investigation lead to the creation of free radicals (in particular oxygen radicals) in the cells.
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