The steps by which molecules in the primordial soup came
together to form the genetic backbone of life are largely
unknown. One approach to finding out is to artificially create
basic life functions in the laboratory and consider if such
conditions might have been possible in the Earth’s past. Writing
in Physical Review Letters, Hubert Krammer and colleagues at the
Ludwig Maximilian University of Munich in Germany show they are
able to drive the replication of segments of tRNA (transfer
ribonucleic acid), the molecule responsible for translating
genetic code into the production of specific proteins, using a
purely thermal process. Krammer et al. begin by rapidly cooling
a solution of four halves of tRNA from high temperatures to so
that the molecules form hairpins—a state where the strand forms
a closed loop on itself, except for a snippet of a sequence of
bases, called a “toe hold.” It is this toe hold, which, in
principle, carries enough information to encode a protein, that
the authors try to protect and r