How Does DNA Separation Work in Cheek Swab Tests?

[lisab]

DNA tests can now be done from a cheek swab. But since our mouths are full of bacteria, how is that DNA separated from human DNA?

 

[Charion]

Simply put, generally it is not. But for the tests you perform a PCR using specific primers so that bacterial contamination is not an issue.

 

[lisab]

Are those primers human-specific?

I'm guessing it's not only bacteria that could contaminate a cheek swab, but food could, as well. It would be quite surprising to take a DNA test and find that you're the offspring of celery and a cow .

 

[Charion]

Yes they are. To be precise they are specific to certain conserved loci in the human genome.