Freeze–thaw cycles could explain how ancient RNA replicated without enzymes

Prebiotic RNA molecules could have copied themselves with the help of freezing and thawing cycles. The finding offers another clue to solve a longstanding puzzle surrounding the ‘RNA world’ model of life’s origins: how RNA strands could self-replicate without the help of enzymes.

Jack Szostak’s group at Harvard University, US, had previously shown that short RNA sequences can act as templates to make further copies without enzymes. When the phosphates on the nucleotide building blocks of RNA were chemically activated in the lab with the highly reactive heterocyclic compound 2-aminoimidazole (2AI), it caused imidazolium bridges to form reactive dinucleotide intermediates, which enabled RNA copying.