DNA from the air

Kirill Stasevich, Science and Life (nkj.ru )

Criminologists actively use DNA analysis: if there are traces of someone's DNA on some surface, it means that a person touched this surface - for example, he could lean on a table, or run his hand along the wall. Or he could not rely and not carry out: in an article in Forensic Science International: Genetics (Puliatti et al., The level of DNA an individual transfers to untouched items in their immediate surroundings), Flinders University staff write that it is not necessary to touch the object with your hand to leave a DNA trace - your DNA can fly over to him by air.

For the experiment, special DNA collection plates were placed around several desktops. The dies stood at a distance of half a meter to five meters, and they stood like that from one day to one and a half months. No one was supposed to touch them. And it turned out that despite the fact that no one touched the dies, the DNA of the person who worked next to them settled on them.

It is easy to guess that the amount of DNA was the greater the longer it was collected. With the distance, everything was not so obvious: most of the DNA was on those dies that stood at a distance of two meters. If there were more than four meters between the die and the desktop, then there was almost no DNA in it. It is clear that DNA will not reach a great distance. But the fact that there was less of it at half a meter than at two meters can perhaps be explained by the fact that DNA just flies a short distance: the air movements produced by man drive it further away.

DNA is a fairly stable molecule. A dead cell, collapsing, leaves DNA in its place, which will also partially collapse, but still not completely - as we know, now they are successfully reading DNA that remained in the soil back in the time of the Neanderthals. We constantly shed some amount of DNA from dead skin cells, exhale it along with water vapor from the lungs, etc., so it's not surprising that even without touching we are able to leave some kind of DNA trace. And criminologists probably need to take this into account: on the one hand, such DNA can help to understand the testimony and facilitate the search for the criminal. But, on the other hand, it can also become garbage, which does not allow you to see the true picture of what happened. And this is not the first study in which the truth of DNA as a witness is questioned: we have already written once that, thanks to the strength and stability of DNA, traces of the DNA of a person who has never touched it can remain on the crime weapon.

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