Scientists discover genetic code that breaks rules of life

Key Points:

• Researchers discovered a freshwater protist, Oligohymenophorea sp. PL0344, that reassigns two traditional stop codons (TAA and TAG) to code for amino acids lysine and glutamic acid, challenging the long-held assumption about the genetic code's stability.
• The discovery was accidental during DNA sequencing method tests and was confirmed by identifying specialized tRNA genes supporting the unusual genetic code, with TGA remaining the sole stop codon in this organism.
• Follow-up studies revealed additional ciliates with independently evolved genetic code changes, such as UAG coding for leucine or glutamine, indicating multiple evolutionary events altering stop codon functions.
• These findings highlight the vast, unexplored genetic diversity among protists and other microorganisms, many of which are difficult to culture in laboratories, revealing new biological rules and evolutionary mechanisms.
• Understanding these genetic code variations has implications for evolutionary biology and synthetic biology, offering insights into genetic code flexibility and potential novel applications in protein engineering.