I have now sequenced my own genome 5 times with an Oxford Nanopore Technologies MinION. This means collecting them from a swab, prepping them for sequencing, running them through a sequencer, then doing analysis over them. Cheek cells are easily accessible and replenish pretty quickly. They are not used for cancer diagnosis, inflammation, or what genes are being activated in other parts of the body (like if you have hives on your chest and want to test what genes are being expressed in the cells...