At the 2014 DEFCON Biohacking village I did exactly that. I gave out like 50 tubes of plasmid, all you had to do is go sequence em to extract the private key, and boom, you get like $200 (or like 15K today...)

Literally nobody did it for a couple years, so I ended up taking out the bitcoin to pay for more DNA synthesis a few years ago. I actually did delete the bitcoin private key though, so I had to pay for sequencing it back out...

Any password-like object has to be changable. And easily.

Same problem as all biometrics. Data about you makes for a bad password. It can make an ok username tho.

Memorising the seedwords of one key + a backup key in a 1 of 2 multisig setup seem to be a good alternative.