XNA

Heredity and evolution, two hallmarks of life, are not limited to DNA and RNA but are likely to be emergent properties of polymers capable of information storage.

-- Synthetic Genetic Polymers Capable of Heredity and Evolution

"There is nothing Goldilocks about DNA and RNA," Holliger told Science. "There is no overwhelming functional imperative for genetic systems or biology to be based on these two nucleic acids.

-- DNA alternative created by scientists

The work heralds the era of synthetic genetics, with implications for exobiology, biotechnology, and understanding of life itself

-- Gerald Joyce

XNA analogues of nucleic acids

P.S. Good overview by Ed Yong