Scientists have long believed that a universal genetic code serves as a blueprint for all life on Earth, dictating the structure and function of organisms from the simplest bacteria to complex humans.

Despite awe-inspiring diversity, nearly every lifeform—from bacteria to blue whales—shares the same genetic code. How and when this code came about has been the subject of much scientific controversy.

Scientists at UC Berkeley have discovered a microbe that bends one of biology’s most sacred rules. Instead of treating a specific three-letter DNA code as a clear “stop” signal, this methane-producing ...