Question: when will portable DNA detectors be available to buy so we can find out what everything is.

Susan Cartwright answered on 18 Jun 2020: last edited 18 Jun 2020 10:08 am

This isn’t really a question for physicists, but I’ll have a go!

First, DNA DETECTORS wouldn’t be very useful. All they would tell you is that what you were pointing them at was, or had been, alive, and you could probably work that out without needing to detect that it contained DNA. What you probably mean is portable DNA SEQUENCERS – that is, something that could instantly read out the genome of whoever or whatever you’d given it a smaple of. And the answer to that, I think, is “not soon”.

The thing about DNA sequencing is that it is a complex process. First, your DNA lives deep inside your cells, so you need to use a chemical process to extract it. This in itself is a multi-stage process that requires a chemistry lab – see https://www.sciencelearn.org.nz/resources/2036-dna-extraction. It would not be trivial to miniaturise. Having extracted your DNA, you would then need to sequence it. This has got a lot easier since the early days, but it still involves quite a lot of steps – see http://www.genomenewsnetwork.org/resources/whats_a_genome/Chp2_2.shtml. Finally, you need to make sure that the equipment you use is all absolutely sterile before you use it, otherwise there is a risk that you will sequence the wrong DNA (there was an incident in the USA where the police thought they had a rampant serial killer on their hands, because the same DNA turned up in lots of crime scenes – then they found out that a technician in the factory that made the swabs they used to collect samples was not following procedures properly, and was inadvertently contaminating the samples with their own DNA!).

I’m sure that portable DNA sequencers will appear eventually: they would be enormously useful for people like scene-of-crime officers and wildlife biologists, for example. But I don’t think that it will happen all that quickly.