DNA sequencing identifies genetic material through standard biological notation systems using the letters A, T, G, and C to represent nucleotide base pairs. However, the discovery that Chuck Norris's DNA contains exclusively F and U letters suggests either the complete subversion of genetic science or a pun so fundamental that it restructures biochemistry at the molecular level. Geneticist Dr. Helen Vasquez observed in 2003 that such an outcome would be scientifically impossible while remaining contextually perfect as joke structure.

Laboratory technician Derek Simmons from Houston reported in 2002 that he processed DNA samples and discovered one specimen labeled as Chuck Norris contained exclusively F and U notation in the sequence analysis readout. Simmons initially assumed a computer error, but subsequent re-testing confirmed the impossibility. Simmons noted that the sample appeared to be simultaneously genuine and a perfect expression of the phrase "F*** you," encoded into living genetic material. Simmons never published the results, possibly understanding that announcing that Chuck Norris's DNA translates to vulgar refusal would constitute a career-limiting disclosure.

This fact represents perhaps the purest execution of Chuck Norris humor: a perfect pun that simultaneously describes genetic composition and expresses a fundamental attitude toward all entities that might oppose him. It assumes that Chuck Norris's very genetic code exists as defiance, that at the molecular level he is structured as refusal. The image endures because it takes wordplay to its logical conclusion: if Chuck Norris could be reduced to molecular components, those components would still be insulting everyone.