The origin of the genetic code is the key to revealing the origin of life on Earth, as it is a prerequisite for the existence of life. More than half a century has passed since the discovery of the genetic code, but its origin is still one of the greatest mysteries. Is the origin of the genetic code truly unknowable? Does the code truly require external design? Here, a hypothesis is proposed, according to which ATP is at the origin of the genetic code by its coevolution with the pristine biochemical system. ATP has several properties that make it suitable as a plausible initiator of the genetic code. First, ATP is the only energetic product of photosynthesis. Second, ATP is at the heart of the extant biochemical systems. Third, ATP serves as a carrier of both energy and information. Fourth, ATP could energetically elongate chains of both polynucleotides and polypeptides, thus providing a bridge between these molecules and eventually mediating prebiotic biochemical innovation from energy transformation to informatization. This hypothesis shows how primitive life emerged through a series of processes from energy to information flow mediated by ATP. Informatization (processes for creating and managing information) was inevitably coupled with structuralization (processes for organizing or incorporating cellular structures), cyclizing polynucleotides and polypeptides into a feedback loop of reciprocal causation. The triplet codon might be only for stereochemical handling of amino acids through, e.g., Watson–Crick pairing interactions. It is only the evolutionary completion of the genetic code from RNA to DNA that, contrary to the central dogma, marked the dawn of cellular life, when Darwinian evolution began to operate. The ATP hypothesis sheds light on the origin of life, together with the formation of both photosynthetic and biochemical systems, which remains largely unknown thus far.
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Subject: Biology and Life Sciences - Biochemistry and Molecular Biology
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